Sensor and method of producing sensor

ABSTRACT

The present invention provides a sensor capable of maintaining an electrical connection between the lead frame and an electrode terminal section of the detection element even when an inadequate external force is applied to a lead frame and a sensor production method capable of preventing the lead frame from buckling and being deformed into an inadequate shape. The lead frame (second lead frame) can inhibit movement of a second frame main body section axially toward a rear end side through engagement of a third locking surface of a second locking section with a second locking groove and can inhibit the second frame main body section from going apart from an inner surface of an insertion hole through engagement of a fourth locking surface of the second frame locking section, which faces an element engagement section side. Namely, even when an external force is applied to the lead frame, movement of the lead frame main body section (second lead frame main body section) can be inhibited and a variation in the relative positions of the lead frame and the detection element can be prevented.

TECHNICAL FIELD

This invention relates to a sensor having a detection element in theform of an axially extending plate and formed with an electrode terminalsection, a separator formed with an element insertion hole for insertionof the detection element, and a metallic terminal member disposedbetween the detection element and an inner surface of the elementinsertion hole of the separator and electrically connected to theelectrode terminal section to form a current path, and a method ofproducing such a sensor.

BACKGROUND TECHNIQUE

Heretofore, it is known a sensor having attached thereto a detectionelement (sensor element) in the form of an axially extending plate andformed with a detection section at a front end side to face an object tobe measured. Enumerated as such a sensor are a gas sensor such as a λ(lambda) sensor, a wide-range air/fuel ratio sensor, oxygen sensor andNOx sensor, and a temperature sensor for detection of temperature.

The plate-shaped detection element is generally configured so as to havea detection section at an axial (longitudinal) front end side and anelectrode terminal section at a rear end side. There is a sensor that isregarded as one having such a detection element and that is configuredto electrically connect a lead frame (metallic terminal member) made ofan electrically conductive material to an electrode terminal section forthereby forming a portion of an electric current path for conduction ofelectrical current between the detection element and an external device.In the meantime, electrical currents such as detection current(detection signal) according to a result of detection by the detectionelement and electrical current for power supply to a heater in case thedetection element has the heater are enumerated for conduction throughthe electrical current path electrically connecting the detectionelement and the external device.

As a sensor having a lead frame is known a sensor configured to use alead frame having a resilient contact portion that serves as aresiliently deformable (deformable by a compressive force) leaf springand hold a detection element within an insertion hole of a separator andin a state where an electrode terminal section of the detection elementis brought into contact with the resilient contact portion of the leadframe (refer to Patent Document 1).

In case of a sensor with such a structure, it becomes possible to makegood the contact condition of the lead frame and the electrode terminalsection of the detection element by using a lead frame configured sothat a resilient contact portion exerts a large resilient force. In themeantime, as a lead frame with a resilient contact portion exerting alarge resilient force are enumerated, for example, a lead frame formedso as to be large in the width size, a lead frame formed so as to belarge in the thickness, etc.

Patent Document 1: Unexamined Japanese Patent Publication No.2001-188060 (FIG. 1, FIG. 6).

However, in case the resilient contact portion of the lead frame exertsan excessively large resilient force, a large pressure more than neededis applied from the lead frame to the detection element at the time ofassembly of the lead frame and the detection element, so that a damageof the detection element such as chipping or breakage may possibly becaused by that pressure.

Further, in the event a lead frame (metallic terminal member) having alarge width size is used as in the above-described prior art sensor, itis necessitated a wide space for disposition of the lead frame, so thatthere arises a problem that such a lead frame is not suited for use in asensor that is needed to be small-sized. Further, in the event a leadframe large in the width size is used for a detection element formedwith a plurality of electrode terminal sections that are small in thewidth size and positioned close to each other, one lead frame is broughtinto contact with all the plurality of electrode terminal sections, sothat there is caused a possibility that a suitable electrical currentpath cannot be formed.

Over against such a problem, it will do to use a lead frame formednarrow in width and small in thickness. By using such a lead frame, itbecomes possible to prevent the lead frame from applying an excessivelylarge pressure to the detection element and make smaller the space fordisposition of the lead frame. Further, by using a lead frame that issmall in the width size, it becomes possible to prevent one lead framefrom extending over a plurality of electrode terminal sections andcontacting them.

However, a lead frame that is formed small in the width size or small inthe thickness has a tendency to decrease in the rigidity.

In case under a condition where such a lead frame that is low in therigidity is disposed in an element insertion hole of a separator, thedetection element is inserted into the element insertion hole, the leadframe is liable to buckle due to the resistance to insertion at thattime and be formed into an inadequate shape. When such deformation ofthe lead frame itself is caused, there arises a problem that suitableelectrical connection between the lead frame and the electrode terminalsection of the detection element cannot be attained or lead frames arebrought into contact with each other to cause shortage.

Further, in case a sensor having a lead frame that is low in rigidityis, for example, subjected to a certain external force in actual use andits external shape is deformed, an inadequate external force is appliedto the lead frame under the influence of the deformation of the sensor,thus possibly causing such a case where the relative positions of thelead frame and the detection element are changed. Namely, since the leadframe that is low in rigidity is liable to be deformed by an externalforce applied thereto, there is a possibility of the electricalconnection between the lead frame and the electrode terminal sectionbeing unable to be maintained suitable when the lead frame is subjectedto an inadequate external force to change the relative positions of thelead frame and the detection element.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoing problemsand has for its object to provide a sensor and a method of producing thesame, which enables a lead frame to be hard to buckle even when aninsertion resistance at the time of insertion of a detection elementinto an element insertion hole of a separator occurs and can maintain anelectrical connection between the lead frame and an electrode terminalsection of the detection element even when an inadequate external forceis applied to the lead frame.

According to an aspect of the present invention, there is provided asensor comprising a detection element in the form of an axiallyextending plate, having a front end side to face an object to bemeasured and formed with an electrode terminal section at a rear endside, a separator made of an insulating material and having an elementinsertion hole accommodating the rear end side of the detection element,and a metallic terminal member interposed between the detection elementand an inner surface of the element insertion hole of the separator,wherein the metallic terminal member is formed from a metallic sheetmaterial and includes an axially extending frame main body section, anelement abutment section extending while being bent to change thedirection of extension, from a front end of the frame main body sectionaxially toward a rear end side of the frame main body section andcontacting the electrode terminal section of the detection elementthereby being electrically connected thereto to form a current path, anda frame locking section provided to a part of the frame main body andhaving a larger width than any other part of the frame main bodysection, and wherein the metallic terminal member is disposed within theseparator so as to be put in a state of being engaged at the framelocking section with the separator.

The sensor is configured to include the metallic terminal member havingthe frame main body section and the element abutment section, and themetallic terminal member forms a current path for an external circuit,with the element abutment section contacting at least partially theelectrode terminal section of the detection element.

In the sensor according to the present invention, the frame main bodysection of the metallic terminal member has the frame locking sectionhaving a width larger than any other part of the frame main bodysection, and the metallic terminal member is disposed within theseparator, with the frame locking section being engaged with theseparator.

By engaging, in this manner, the frame locking section formed at aportion of the frame main body section with the separator, it becomespossible to inhibit movement of the frame main body section axiallytoward a rear end side with respect to the separator or in the directionapart from the inner surface of the element insertion hole. Accordingly,since movement of the main body section can be suppressed even in thecase an unsuitable external force is applied to the metallic terminalmember, it becomes possible to prevent effectively a variation in therelative positions of the metallic terminal member and the detectionelement that are disposed within the separator.

Further, since the frame locking section is formed so as to be larger inthe width than any other part of the frame main body section, therigidity of the frame main body section can be retained even in the casethe frame main body section is designed so as to be small in width(width size) and the locking force of the frame locking section withrespect to the separator can be attained effectively. Further, bydesigning the frame locking section so as to be large in width, theframe locking section can, for example, be bent freely and thereforethere is obtained such a merit that the design freedom of the framelocking section in engagement with the separator can be large.

In the meantime, the term “width (width size)” is herein used toindicate the size in the direction perpendicular to the axial directionand further to the direction of an intervening space between the elementabutment section and the frame main body section.

Further, in the above-described sensor, it is preferable that the framelocking section has an extension portion that extends in the directionapart from the element abutment section and is bent at least once ormore at an intermediate part thereof in a way as to change its directionof extension, the fame locking section being larger in width than theabove-described other part of the frame main body section when theextension portion is developed in the width direction of the remainingportion of the frame main body section.

In the present invention, the frame locking section provided to a partof the frame main body section has the extension portion that extends inthe direction apart from the element abutment section and is bent atleast once or more at an intermediate part thereof. By constructing sothat the frame locking section includes such an extension portion, itbecomes possible to prevent the metallic terminal member (frame mainbody) itself from being formed with a portion that is excessively largein width even in the case the frame locking section is designed so as tobe larger in width than any other part of the frame main body section.Accordingly, in case the metallic terminal member is disposed within theseparator, a large space for disposition thereof is not necessitated,thus making it possible to make the sensor small-sized effectively.

Further, in any of the above-described sensors, it is preferable thatthe separator includes a locking groove for engagement with the framelocking section or a partition wall portion.

In engagement of the frame locking section with the separator, the framelocking section can be engaged with the separator more assuredly byproviding the separator with the locking groove and accommodating theframe locking section within the locking groove thereby engaging theframe locking section with the locking groove.

Further, by disposing the partition wall portion between the elementinsertion hole and at least a part of the frame locking section, theframe locking section can be engaged with the separator easily.

In the meantime, it is preferable to form the above-described lockinggroove or/and the partition wall portion at the front end surface of theseparator for ease of accommodation of the frame locking section of themetallic terminal member.

According to another aspect of the present invention, there is provideda sensor comprising a detection element in the form of an axiallyextending plate, having a front end side to face an object to bemeasured and formed with an electrode terminal section at a rear endside, a separator made of an insulating material and having an elementinsertion hole accommodating the rear end side of the detection element,and a metallic terminal member interposed between the detection elementand an inner surface of the element insertion hole of the separator,wherein the metallic terminal member is formed from a metallic sheetmaterial and having a frame main body section extending axially, anelement abutment section extending while being bent to change thedirection of extension, from a front end of the frame main body sectionaxially toward a rear end side of the frame main body section andcontacting the electrode terminal section of the detection elementthereby being electrically connected thereto to form a current path, anda frame locking section provided to a part of the frame main bodysection, and wherein the separator has a locking groove at a front endsurface thereof and the frame locking section is engaged with thelocking groove.

The sensor according to another aspect of the present invention is alsoconfigured to include the metallic terminal member having the frame mainbody section and the element abutment section. To a part of the framemain body section is provided the frame locking section. By engaging theframe locking section with the separator, the metallic terminal memberis disposed within the separator. By engaging the frame locking sectionprovided to a part of the frame main body section with the separator,movement of the frame main body section can be suppressed even in thecase an inadequate external force is applied to the metallic terminalmember, and a variation in the relative positions of the metallicterminal member and the detection element that are disposed within theseparator can be prevented effectively.

Further, in the sensor of this aspect of the invention, for engagementof the frame locking section with the separator, the separator has thelocking groove at the front end surface thereof and the frame lockingsection is engaged with the locking groove.

By accommodating the frame locking section within the locking grooveformed in the separator and thereby engaging them, the frame lockingsection can be engaged with the separator assuredly. Further, by formingthe locking groove at the front end surface of the separator, the framelocking section can be accommodated within the locking groove easily.

According to a further aspect of the present invention, there isprovided a sensor comprising a detection element in the form of anaxially extending plate, having a front end side to face an object to bemeasured and formed with an electrode terminal section at a rear endside, a separator made of an insulating material and having an elementinsertion hole accommodating the rear end side of the detection element,and a metallic terminal member interposed between the detection elementand an inner surface of the element insertion hole of the separator,wherein the metallic terminal member is formed from a metallic sheetmaterial and having a frame main body section extending axially, anelement abutment section extending while being bent to change thedirection of extension, from a front end of the frame main body sectionaxially toward a rear end side of the frame main body section andcontacting the electrode terminal section of the detection elementthereby being electrically connected thereto to form a current path, anda frame locking section having a first locking surface facing axiallytoward a rear end side of the frame main body section and a secondlocking surface facing in the direction of an intervening space betweenthe frame main body section and the element abutment section and towardthe element abutment section, and wherein the separator has a lockinggroove for disposition of the frame locking section and engages at aninner wall surface of the locking groove with the first locking surfaceand the second locking surface.

The sensor of this aspect of the invention is also configured so as toinclude the metallic terminal member having the frame main body sectionand the element abutment section. The metallic terminal memberconstitutes part of a current path for connection with an externalcircuit when at least a portion of the element abutment section isabuttingly engaged with the electrode terminal section.

In the sensor of this aspect of the invention, the metallic terminalmember includes the frame locking section having the first lockingsurface and the second locking surface and is configured so that theframe locking section is disposed in the locking groove of the separatorto engage the first locking surface and the second locking surface withthe inner wall surface of the locking groove.

Engagement of the first locking surface of the frame locking sectionwith the inner wall surface of the locking groove makes it possible toinhibit the frame main body section from moving axially toward the rearend side. Further, engagement of the second locking surface of the framelocking section with the inner wall surface of the locking groove makesit possible to inhibit the frame main body section from moving in thedirection apart from the inner surface of the element insertion hole.Namely, even in the case an inadequate external force is applied to themetallic terminal member, movement of the frame main body section can beinhibited, thus making it possible to prevent the relative positions ofthe metallic terminal member and the detection element from beingvaried.

Thus, according to the present invention, in use of a metallic terminalmember that is formed so as to be smaller in the width size or smallerin the thickness, it becomes possible to prevent the relative positionsof the metallic terminal member and the detection element from beingvaried and maintain electrical connection between the metallic terminalmember and the electrode terminal section suitably even in the case aninadequate external force is applied to the metallic terminal member.

In the meantime, the locking groove is preferably formed at the frontend surface of the separator for easy accommodation of the frame lockingsection of the metallic terminal member therewithin.

Further, in the above-described sensor, the metallic terminal member ispreferably configured so that a frame abutment portion of the elementabutment section, which is positioned closer to a rear end of the framemain body section than an end portion of the element abutment section,which is connected to the front end of the frame main body section, isnot abuttingly engaged with the frame main body section when themetallic terminal member is in a free state before being electricallyconnected to the electrode terminal section of the detection element,while being configured so that the frame abutment portion is abuttinglyengaged with the frame main body section when the element abutmentsection is electrically connected to the electrode terminal section andresiliently deformed toward the frame main body section.

The metallic terminal member is configured so that when in a free state,the frame abutment portion of the element abutment section does notengage the frame main body section and the element abutment section issupported at one place (i.e., an end portion (hereinafter also referredto as “connection side end portion” connected to the front end of theframe main body section) by the frame main body section. For thisreason, the metallic terminal member is configured, when in a state ofthe frame abutment portion of the element abutment section being notabuttingly engaged with the frame main body section, so as to be pressedagainst the electrode terminal section of the detection element by thestress caused by resilient deformation of a portion of the elementabutment section, which is positioned adjacent the connection side endportion. The element abutment section continues resilient deformationtoward the frame main body section to cause the frame abutment portionto abuttingly engage the frame main body section. By this, the elementabutment section is supported at least at two places, i.e., at theconnection side end portion and the frame abutment portion, by the framemain body section.

As described above, the metallic terminal member provided to the sensorof the present invention is configured so that the pressure that urgesthe metallic terminal member against the detection element variesdepending upon whether or not the frame abutment portion of the elementabutment section is abuttingly engaged with the frame abutment portion.More specifically, the metallic terminal member is configured so thatthe pressure that urges the metallic terminal member against theelectrode terminal section of the detection element when the frameabutment portion of the element abutment section is abuttingly engagedwith the frame main body section (two-point support condition) becomeslarger as compared with that when the frame abutment portion of theelement abutment section is not abuttingly engaged with the frame mainbody section (one-point support condition).

The element abutment section that is brought into the two-point supportcondition as described above when the sensor is completed produces alarger stress by resilient deformation thereof as compared with thatwhen in one-support condition. Namely, the metallic terminal member canpress the element abutment section against the electrode terminalsection of the detection element with a larger stress and attain a goodelectrical condition between the metallic terminal member and theelectrode terminal section of the detection element.

Further, in any of the sensors described above, it is preferable thatthe frame locking section includes a first connection portion extendingfrom a front end side portion of the frame main body section in thedirection apart from the element abutment section, a second connectionportion extending from an end of the first connection portion axiallytoward the front end side, and a wide protrusion portion protruding fromthe second connection portion in the width direction of the secondconnection portion, wherein the first connection portion is formed withthe above-described first locking surface, and the wide protrusionportion is formed with the second locking surface.

The first connection portion of the frame locking section provided tothe sensor is configured so as to extend from the front end side portionof the frame main body section in the direction apart from the elementabutment section. Since the direction of extension of the firstconnection portion is not parallel with the axial direction of the framemain body section, the first connection portion at least has a part(surface) that faces axially toward the rear end side of the frame mainbody section. Since that part can be used as the first locking surface,it becomes possible to inhibit the frame main body section (metallicterminal member) from moving axially toward the rear end side thereof.

Further, the second connection portion of the frame locking section isconfigured so as to extend from the end of the first connection partaxially toward the front end, and the direction of extension of thesecond connection portion is not parallel with the direction of anintervening space between the frame main body section and the elementabutment section. Thus, the second connection portion at least has apart (surface) that faces the element abutment section side. Since thatpart can be used as the second locking surface, it becomes possible toinhibit the frame main body section (metallic terminal member) frommoving in the direction apart from the inner surface of the elementinsertion hole through engagement of at least a part of the secondconnection portion with the inner surface of the locking groove of theseparator.

Namely, the metallic terminal member having the first connection portionand the second connection portion can prevent movement of the frame mainbody section even when an inadequate external force is applied thereto,thus making it possible to prevent the relative positions of themetallic terminal member and the detection element from being varied.

In the meantime, the wide protrusion portion can be formed, for example,so as to extend from a side surface of the second connection portion.Further, the wide protrusion part can be formed only at one side surfaceor each of the opposite side surfaces of the second connection portion.In the meantime, the term “width direction” is intended to indicate thedirection perpendicular to the axial direction and further to thedirection of an intervening space between the element abutment sectionand the frame main body section.

Further, in the above-described sensor, it is preferable that the wideprotrusion or portions are formed so as to be asymmetrical about acenter axis of the second connection portion.

As such sensors are enumerated an example in which the wide protrusionportion is formed only at one side surface of the second connectionportion, an example in which the wide protrusion portions are formed atthe respective side surfaces of the second connection portion and thewidth size (protrusion size) of one of the wide protrusion portions isformed so as to be larger as compared with that of the other, etc.

In the example of the sensor in which the wide protrusion portion isprovided to only one side surface of the second connection portion, itbecomes possible to inhibit movement of the frame main body sectionassuredly by the effect of abutting engagement of the wide protrusionportion with the locking groove of the separator even when an inadequateexternal force is applied to the metallic terminal member. Since theother side surface of the second connection portion is not formed withthe wide protrusion portion, it will suffice that the locking groove ofthe separator has a region for abuttingly engagement with one wideprotrusion portion. For this reason, as compared with the case where thesecond connection portion has the wide protrusion portions at the bothside surfaces, a locking groove portion for engagement with the wideprotrusion portion can be smaller in size and therefore there can beattained such an advantage that in the case where a plurality ofmetallic terminal members are arranged side by side the distance betweenthe adjacent metallic terminal members can be made smaller.

Further, in an example of the sensor in which the second connectionportion has the wide protrusion portions at the both side surfaces, itbecomes possible to inhibit movement of the frame main body sectionassuredly by the effect of abutting engagement of the wide protrusionportions provided to the second connection portion with the lockinggroove of the separator even when an inadequate external force isapplied to the metallic terminal member. Since the wide protrusionportion provided to one of the both side surfaces of the secondconnection portion is smaller in the protrusion size, it becomespossible to make the portion of the locking groove of the separator forabutting engagement with the wide protrusion portion smaller in size,and therefore there can be attained such an advantage that in the casewhere a plurality of metallic terminal members are arranged side by sidethe distance between the adjacent metallic terminal members can be madesmaller.

By making smaller the space for disposition of the metallic terminalmembers, the density of the number of the metallic terminal membersdisposed per a unit length can be made higher and therefore the numberof the metallic terminal members that can be disposed in the elementinsertion hole of the same size can be increased. For this reason, incase the detection element has a number of electrode terminal sections,the metallic terminal members can be connected to the respectiveelectrode terminal sections assuredly.

In the meantime, the term “width size (protrusion size)” of the wideprotrusion portion is intended to indicate the size from the end of thewide protrusion portion for connection with the second connectionportion to the end positioned at the outer side with respect to thewidth direction of the second connection portion.

Further, in any of the above-described sensors, it is preferable thatthe frame locking section includes a first extension portion extendingfrom a front end side portion of the frame main body section in thedirection apart from the element abutment section and a second extensionportion extending from an end of the first extension portion on the sideremoter from the element abutment section in parallel with the framemain body section, at least one of the first extension portion and thesecond extension portion is formed with the first locking surface andthe second extension portion is formed with the second locking surface.

The first extension portion of the frame locking section provided to thesensor extends from the front end side part of the frame main bodysection in the direction apart from the element abutment section and thedirection of extension is not parallel with the axial direction of theframe main body section, so that the first extension portion has atleast a part (surface) that faces axially toward the rear end side ofthe frame main body section. Since that part can be used as the firstlocking surface, it becomes possible to inhibit the frame main bodysection (metallic terminal member) from moving axially toward the rearend side through engagement of at least a part of the first connectionportion with the inner wall surface of the locking groove of theseparator.

Further, since the second extension portion of the frame locking sectionextends parallel with the frame main body section and the direction ofextension is not parallel with the direction of an intervening spacebetween the frame main body section and the element abutment section,the second extension portion has at least a part that faces the elementabutment section side. Since that part can be used as the second lockingsurface, it becomes possible to inhibit the frame main body section(metallic terminal member) from moving in the direction apart from theinner surface of the element insertion hole through engagement of atleast a part of the second connection portion with the inner wallsurface of the locking groove of the separator.

Namely, the metallic terminal member provided with the frame lockingsection having the first extension portion and the second extensionportion can inhibit movement of the frame main body section and preventthe relative positions of the metallic terminal member itself and thedetection element from being varied even when subjected to an inadequateexternal force.

In the meantime, the direction of extension of the second extensionportion will suffice if it enables the second extension portion to haveat least a part (surface) that faces in the direction of an interveningspace between the frame main body section and the element abutmentsection and toward the element abutment section, and is not limited to aparticular direction. For example, the second extension portion may bedisposed so as to extend from the axial front end side or the axial rearend side of the frame main body section.

Further, in the above-described sensors, it is preferable that at leasttwo of the locking sections are provided so as to extend from differentplaces of a front end side portion of the frame main body section.

By using the metallic terminal member having at least two frame lockingsections, it becomes possible to increase the area of an engagementportion at which the frame locking sections are engaged with theseparator (the inner wall surface of the locking groove), thus making itpossible to inhibit movement of the frame main body section moreassuredly and prevent a variation in the relative positions of themetallic terminal member and the detection element more assuredly evenwhen an inadequate external force applied to the metallic terminalmember becomes larger.

As an example of a metallic terminal member having two frame lockingsections can be enumerated, for example, a metallic terminal memberconfigured to have frame locking sections that extend from the endportions opposed in the width direction of the frame main body section.Further, the frame locking section can be formed so as to have a nearlyL-shaped cross section with respect to a sectional plane perpendicularto the axial direction and thereby can have the first extension portionand the second extension portion. Further, in the metallic terminalmember having a plurality of frame locking sections, it is notnecessitated to limit the extension directions of the second extensionportions of each frame locking section to the same direction but thesecond extension portions of each frame locking section may be formed soas to extend in the different directions in accordance with the shape ofthe locking groove of the separator.

Further, in any of the above-described sensors, it is preferable thatthe frame locking section includes a first frame connection portionextending from a front end side portion of the frame main body sectionin the direction apart from the element abutment section, a second frameconnection portion extending from an end of the first connection portionon the side remoter from the element abutment section, axially towardthe rear end side of the frame main body section, and a third frameconnection portion extending from the end of the second connectionportion on the side opposite to the side for connection with the firstframe connection portion so as to be connected to the element abutmentsection, wherein the first frame connection portion is formed with thefirst locking surface and the second frame connection portion is formedwith the second locking surface.

Since the first frame connection portion of the frame locking sectionprovided to the sensor is configured so as to extend from the front endside portion of the frame main body section in the direction apart fromthe element abutment section and the direction of extension thereof isnot parallel with the axial direction of the frame main body section,the first frame connection portion has at least a part (surface) thatfaces axially toward the rear end side of the frame main body section.Since that part can be used as a first locking surface, movement of theframe main body section (metallic terminal member) axially toward therear end side can be inhibited through engagement of at least a part ofthe first connection portion with the inner wall surface of the lockinggroove of the separator.

Further, since the second frame connection portion of the frame lockingsection is configured so as to extend from an end of the first frameconnection portion axially toward the rear end side and the direction ofextension thereof is not parallel with the direction of an interveningspace between the frame main body section and the element abutmentsection, the second frame connection portion has at least a part(surface) that faces the element abutment side. Since that part can beused as second locking surface, movement of the frame main body section(metallic terminal member) in the direction apart from the inner surfaceof the element insertion hole can be inhibited through engagement of atleast a part of the second connection portion with the inner wallsurface of the locking groove of the separator.

Namely, the metallic terminal member provided with the frame lockingsection having the first frame locking section and the second framelocking section can inhibit movement of the frame main body section evenwhen an inadequate external force is applied thereto and therefore canprevent the relative positions of the metallic terminal member itselfand the detection element from being varied.

Further, in any of the above-described sensors, it is preferable thatthe detection element has a plural number of the electrode terminalsections, a plural number of the metallic terminal members are providedin accordance with the number of the electrode terminal sections andconnected to the different lead wires, respectively, and the elementinsertion hole of the separator is formed so as to extend axiallythroughout thereof and sized so as to enable all of the lead wires to beinserted thereinto.

Namely, the separator does not have one lead wire insertion hole foreach lead wire but is configured so as to employ such an elementinsertion hole that is sized to enable all of the lead wires to beinserted thereinto as a lead wire insertion hole. In this instance,since the element insertion hole has a larger opening sectional area ascompared with the lead wire insertion hole for each lead wire, itbecomes possible to attain a larger spacing interval between the leadwire and the inner surface of the element insertion hole. By this, itbecomes difficult for the lead wire to be caught by the inner wall ofthe element insertion hole at the time of the work for insertion, thusmaking it possible to prevent a coating material from being cut off bythe lead wire at the time of the work for lead wire insertion and reducethe complexity of the work for insertion of the lead wire into theelement insertion hole of the separator.

According to a further aspect of the invention, there is provided amethod of producing a sensor including a detection element in the formof an axially extending plate, having a front end side to face an objectto be measured and formed with an electrode terminal section at a rearend side, a separator made of an insulating material and having anelement insertion hole accommodating the rear end side of the detectionelement, and a metallic terminal member interposed between the detectionelement and an inner surface of the element insertion hole of theseparator, wherein the metallic terminal member is formed from ametallic sheet material and having a frame main body section extendingaxially, an element abutment section extending while being bent tochange the direction of extension from a front end of the frame mainbody section axially toward a rear end side of the frame main bodysection and contacting the electrode terminal section of the detectionelement thereby being electrically connected thereto to form a currentpath, and a frame locking section having a first locking surface facingaxially toward a rear end side of the frame main body and a secondlocking surface facing in the direction of an intervening space betweenthe frame main body section and the element abutment section and towardthe element abutment section, wherein the separator has a locking groovefor disposition of the frame locking section, the method comprising afirst step of disposing at least the element abutment section of themetallic terminal member within the element insertion hole of theseparator and disposing the frame locking section within the lockinggroove, thereby engaging the first locking surface and the secondlocking surface with the inner wall surface of the locking groove, asecond step of disposing the rear end side of the detection element, atwhich the detection element is formed with the electrode terminalsection, at a front end side of the separator, and a third step ofinserting the rear end side of the detection element into the elementinsertion hole of the separator and bringing the electrode terminalsection of the detection element and the metallic terminal member intocontact with each other.

In the sensor production method, the frame locking section of themetallic terminal member is disposed in the locking groove of theseparator to engage the first locking surface and the second lockingsurface with the inner surface of the locking groove. By engaging thefirst locking surface and the second locking surface with the innersurface of the locking groove in this manner, it becomes possible torestrict movement of the frame main body section in the direction of theaxial rear end side. Further, by engaging the second locking surface ofthe frame locking section with the inner surface of the locking groove,it becomes possible to restrict movement of the frame main body sectionin the direction apart from the inner surface of the element insertionhole.

For this reason, in case of insertion of the detection element into theelement insertion hole of the separator in the third step, the firstlocking surface and the second locking surface are engaged with theinner surface of the locking groove even when an external force due to afriction force (resistance to insertion) caused between the detectionelement and the metallic terminal member (specifically, element abutmentsection) is applied to the metallic terminal member, thus making itpossible to inhibit movement of the frame main body section (metallicterminal member).

Thus, by the sensor production method of the present invention, therelative positions of the metallic terminal member and the electrodeterminal section of the detection can be prevented from becominginadequate at the time of the work for inserting the detection elementinto the separator, and the metallic terminal member and the electrodeterminal section of the detection element can be electrically connectedassuredly. Further, since movement of the metallic terminal member atthe time of production of the sensor is restricted through engagement ofthe frame locking section with the locking groove, buckling of themetallic terminal member is hard to be caused, thus making it possibleto prevent the metallic terminal member and the electrode terminalsection of the detection element from being disabled to be electricallyconnected.

Further, in the above-described sensor production method, it ispreferable that the metallic terminal member is configured so that theframe abutment portion of the element abutment section, which ispositioned closer to the rear end than the end portion of the elementabutment section for connection with the front end of the frame mainbody section, is not abuttingly engaged with the frame main body sectionwhen the element abutment section is in a free state before beingelectrically connected to the electrode terminal section of thedetection element, while being configured so that the frame abutmentportion is abuttingly engaged with the frame main body section when themetallic terminal member is electrically connected to the electrodeterminal section to cause the element abutment section to resilientlydeform toward the frame main body section, wherein it is preferable thatthe first step includes disposing the metallic terminal member in astate of not receiving any external force within the element insertionhole of the separator and the third step includes inserting thedetection element into the element insertion hole while pushing thedetection element against the element abutment section, therebyresiliently deforming the element abutment section toward the frame mainbody section and abuttingly engaging the frame abutment portion of theelement abutment section with the frame main body section.

The metallic terminal member is configured so as to produce a variablepressure for pressing the metallic terminal member against the detectionelement depending upon whether or not the frame abutment portion of theelement abutment section is abuttingly engaged with the frame abutmentportion. More specifically, the metallic terminal member is configuredso as to produce a larger pressure for pressing the metallic terminalmember itself against the electrode terminal section of the detectionelement when the frame abutment portion of the element abutment sectionis not abuttingly engaged with the frame main body section (one-pointsupport state) as compared with that produced thereby when the frameabutment portion of the element abutment section is abuttingly engagedwith the frame main body section (two-point support state).

By this, in case of assembly of the metallic terminal member and thedetection element in a sensor production process, the element abutmentsection of the metallic terminal member is pressed against the electrodeterminal section of the detection element with a relatively smallerforce in the first half of the assembly work, thus making it possible toinhibit an excessively large pressure from being applied to thedetection element and causing breakage thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an overall structure of a wide-rangeair/fuel ratio sensor according to an embodiment;

FIG. 2 is a perspective view depicting a schematic structure of adetection element;

FIG. 3 is a perspective view depicting an external appearance of a leadframe;

FIG. 4 is a perspective view of an external appearance of a separator;

FIG. 5 is a perspective view of a separator in a state where a leadframe is disposed in an insertion hole;

FIG. 6 is a view for illustrating states of deformation of the leadframe within the insertion hole at the time of a work for inserting thedetection element into the separator;

FIG. 7 is a perspective view of an intermediate assembly in a statewhere a rear end side of the detection element is protruded from a rearend portion of a metallic member and a rear end portion of a ceramicsleeve;

FIG. 8 is a perspective view showing an external appearance of a secondseparator;

FIG. 9 is a perspective view showing external appearances of a thirdlead frame and fourth lead frame;

FIG. 10 is a perspective view showing an external appearance of a thirdseparator;

FIG. 11 is a perspective view showing external appearances of a fifthlead frame and sixth lead frame;

FIG. 12 is a perspective view showing an external appearance of a fourthseparator; and

FIG. 13 is a perspective view showing an external appearance of aseventh lead frame.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described hereinafter byreference to drawings.

In the meantime, according to this embodiment will be described a kindof gas sensor, specifically a wide-range air/fuel ratio sensor 2(hereinafter also referred to as air/fuel ratio sensor 2) composed of adetection element (gas sensor element) for detecting a particular gaswhich is an object to be measured and contained in an exhaust gas, foruse in an air/fuel ratio feedback control in automotive or other variouskinds of internal combustion engines.

FIG. 1 is a sectional view showing an overall structure of the air/fuelratio sensor 2 according to an embodiment of the present invention.

The air/fuel ratio sensor 2 includes a detection element 4 in the formof a plate extending in an axial direction (vertical direction in thedrawing), a tubular metallic housing 102 accommodating the detectionelement 4 in a way as to allow a front end portion of the detectionelement 4 to protrude therefrom, a ceramic sleeve 6 disposed between thedetection element 4 and the metallic housing 4, and a separator 82 madeof alumina and disposed in a way as to surround a rear end portion ofthe detection element 4.

The detection element 4 is in the form of an axially extending plat andformed at a front end side (lower side in the figure) to face a gas thatis an object to be measured, with a detection section 8 covered by aprotection layer and at a first plate surface 21 and a second platesurface 23 of outer surfaces of a rear end side (upper side in thefigure), which first and second plate surfaces have a relation between afront side and a rear side, with electrode terminal sections 30, 31, 32,34 and 36 (refer to FIG. 2). Five lead frames (metallic terminalmembers) 10 are disposed between the detection element 4 and theseparator 82 and electrically connected to the electrode terminalsections 30, 31, 32, 34 and 36, respectively. Further, the lead frames10 are electrically connected at the rear end sides thereof to leadwires 46 that are disposed inside the sensor through movement from theoutside and constitute electrical paths for current flowing between anexternal circuit to which the lead wires 46 are connected and theelectrode terminal sections 30, 31, 32, 34 and 36.

The metallic housing 102 has at an outside surface a threaded section103 for fixation to an exhaust pipe and is formed into a nearly tubularshape having inside thereof a through hole extending axiallytherethrough. Further, the metallic housing 102 is configured so as toallow the detection section 8 to protrude from the front end side andhold therewithin the detection element 4 in a way as to allow theelectrode terminal sections 30, 31, 32, 34 and 36 to protrude from therear end side.

To the front end side (lower side in FIG. 1) outer periphery of themetallic housing 102 is attached by welding or the like an outerprotector 42 and inner protector 43 which are made of metal (forexample, stainless steel or the like) to constitute a dual-wall and havea plurality of holes.

Further, a separator 82 is disposed around the rear end side (upper sidein FIG. 1) of the detection element 4, which protrudes from a rear endportion 104 of the metallic housing 102 and accommodates the electrodeterminal sections 30, 31, 32, 34 and 36 within an insertion hole 84.

To the rear end side outer periphery of the metallic housing 102 isfixedly attached an outer tube 44. At the rear end side (upper side inFIG. 1) opening portion of the outer tube 44 is disposed a grommet 50,and lead wires 46 are inserted into lead wire insertion holes 61 of thegrommet 50.

Within a through hole 109 of the metallic housing 102 are placed oneupon another an annular ceramic holder 106, a power filling layer 108(hereinafter also referred to as talcum ring 108), an auxiliary sleeve110 and a ceramic sleeve 6 in this order from the front end side to therear end side in a way as to surround the circumferential periphery ofthe detection element 4. These laminated layers are fixedly held betweena shoulder portion 107 and a rear end portion 104 by caulking by way ofpacking 129 and a caulking ring 112.

In this connection, a perspective view of the schematic structure of thedetection element 4 is shown in FIG. 2. In the meantime, in FIG. 2, anaxially intermediate portion of the detection element 4 is omitted.

The detection element 4 includes an element section 20 formed into anaxially (in the horizontal direction in FIG. 2) extending plate shapeand a heater 22 formed into a similar axially extending plate shapeextending, which are placed one upon another to allow the detectionelement to be formed into a plate shape having a rectangular crosssection. In the meantime, since the detection element 4 used as theair/fuel ratio sensor 2 is of the type known in the art, the detaileddescription of the inside structure, etc. are omitted but the schematicstructure thereof is as follows.

Firstly, the element section 20 consists of an oxygen concentration cellincluding porous electrodes formed on the opposite sides of a solidelectrolytic substrate, an oxygen pump cell including porous electrodessimilarly formed on the opposite sides of a solid electrolyticsubstrate, and a spacer placed between the cells for forming a hollowgas measurement chamber. The solid electrolytic substrate is made of asolid solution of zirconia and yttria as a stabilizer, and the porouselectrode is made of a material containing Pt as a major component.Further, the spacer that forms the gas measurement chamber is made of amaterial containing alumina as a major component, and one of the porouselectrodes of the oxygen concentration cell and one of the porouselectrodes of the oxygen pump cell are disposed so as to be exposed tothe hollow measurement gas chamber. In the meantime, the measurement gaschamber is formed so as to be positioned at the front end side of theelement section 20, and a portion of the element section, at which themeasurement gas chamber is formed, corresponds to the detection section8.

Then, the heater 22 is formed so as to have a heating resistor patternthat is made of a material containing Pt as a major component andinterposed between insulating substrates made of alumina as a majorcomponent.

The element section 20 and the heater 22 are connected to each other byinterposing therebetween a ceramic layer (e.g., zirconia system ceramicor alumina system ceramic). Further, on at least the surface of theelectrodes of the detection element 4, which is exposed to an object tobe measured (in this embodiment, exhaust gas) is formed a protectionlayer (not shown) made of porous ceramic for protection from poisoning.In the meantime, in this embodiment, the protection layer covers all thefront end side surface of the detection element, which includes thesurface of the electrode to be exposed to the exhaust gas.

Such a detection element 4, as shown in FIG. 2, is formed with threeelectrode terminal sections 31, 32, 33 at the rear end side (theright-hand side in FIG. 2) of the first plate surface 21 and twoelectrode terminal sections 34, 36 at the rear end side of the secondplate surface 23. The electrode terminal sections 30, 31, 32 are formedat the element section 20, one of which electrode terminal sections iselectrically connected, in the manner of common use, to one of theporous electrodes of the oxygen concentration cell that is exposed tothe inside of the measurement gas chamber and one of the porouselectrodes of the oxygen pump cell. Further, remaining two of theterminal electrodes 30, 31, 32 are electrically connected to the otherof the porous electrodes of the oxygen concentration cell and the otherof the porous electrodes of the oxygen pump cell. Further, the electrodeterminal sections 34, 36 are formed at the heater 22 and connected tothe opposite ends of the heating resistor pattern by way of a via (notshown) extending crosswise in the thickness direction of the heater 22,respectively.

Then, the separator will be described. FIG. 4 is a perspective viewshowing the external appearance of the separator 82 when observed fromthe front end side thereof.

As shown in FIG. 4, the separator 82 is made of alumina and formed intoa tubular shape so as to have an insertion hole 84 extending axiallytherethrough while being provided with a flange portion 83 protrudingradially outward from an external surface thereof. The separator 82 isdisposed inside the outer tube 44 by being abuttingly engaging at theflange portion 83 with an outer tube side support portion 64 of theouter tube 44. In the meantime, the outer tube side support portion 64is formed so as to protrude inward of the outer tube 44 (refer to FIG.1).

At the inner wall surface of the insertion hole 84, which faces thefirst plate surface 21 (not shown), and at two places thereof are formedfirst rib portions 87 that protrude inward. The first rib portions 87are provided so as to serve as lead frame boundary portions inside theinsertion hole, which form boundaries of three first frame dispositiongrooves 86 for disposing three lead frames 10 in a state of beingelectrically insulated from each other. The three first framedisposition grooves 86 are formed at the first plate surface 21 of thedetection element 4 and at the positions corresponding to the electrodeterminal sections 30, 31, 32, respectively.

Further, at the inner wall surface of the insertion hole 84, which facesthe second plate surface 23 (not shown) of the detection element 4, andat one place thereof is formed a second rib portion 89 that protrudesinward. The second rib portion 89 is provided to serve as a lead frameboundary portion inside the insertion hole, which forms a boundary oftwo second frame disposition grooves 88 for disposing the two leadframes 10 in a state of being electrically insulated from each other.The second disposition grooves 88 are formed at the second plate surface23 of the detection element 4 and at the positions corresponding to theelectrode terminal sections 34, 36.

The first rib portions 87 and second rib portion 89 have a function ofpreventing the lead frames 10 disposed in the adjacent frame dispositiongrooves from contacting each other and can prevent the electrical pathfrom becoming defective by preventing the lead frames 10 from beingelectrically connected to each other.

Further, the separator 82 has at the front end surface thereof (thisside surface in the figure) first locking grooves 90 and a secondlocking groove 91 that are formed so as to be joined to the front endside opening portion of the insertion hole 84.

The first locking grooves 90 are formed into a nearly L-shape whenobserved from the front end side and configured so as to disposetherewithin a first frame locking section 19 of the lead frame 10, whichwill be described later. In the meantime, the first locking grooves 90are formed at two places where they are connected to two of the threefirst frame disposition grooves 86, which are formed at the oppositesides and at two places where they are connected to the two second framedisposition grooves 88.

The second locking groove 91 consists of a narrower groove portion 93formed between two protrusion portions 92 and a wider groove portion 94formed at a portion of the insulation contact member 82, which ispositioned at a radially outer side of the narrower groove portion 93,and is configured so as to dispose therewithin a second frame lockingsection 219 of the lead frame 10, which will be described later. In themeantime, the protrusion portion 92 is formed so as to be continuousfrom an end of the first rib portion 87. Further, the second lockinggroove 91 is formed at one place where it is connected to one firstframe disposition groove 86 that is formed in the middle of the threefirst frame disposition grooves 86.

Further, the separator 82 has a partition wall portion. The partitionwall portion is formed between the first locking groove 90 and theinsertion hole 84. At the time of installation of the lead frame 10, thepartition wall is positioned between the first frame locking section 19that is inserted into the first locking groove 90 and the elementinsertion hole to perform a function of preventing falling off of thefirst frame locking section 19.

Then, the lead frame 10 will be described. FIG. 3 is a perspective viewshowing the external appearance of the lead frame 10. In the meantime,the air/fuel ratio sensor 2 of this embodiment is configured to includetwo kinds of lead frames 10 that are different in the shape of the framelocking section (the first lead frame 11 on the left-hand side of FIG. 3and the second lead frame 211 on the right-hand). Further, the leadframe 10 is made of a known material (e.g., inconel, stainless steel orthe like) that can maintain the resiliency (springing resilience) evenwhen exposed to a high temperature repeatedly.

First, the first lead frame 11 will be described.

The first lead frame 11 includes a frame main body section 12 formedfrom an axially extending plate, an element abutment section 16extending while being bent, from a front end of the frame main bodysection 12 so as to be disposed between the frame main body section 12and the detection element 4 and having a portion at which it isabuttingly engaged with the electrode terminal section of the detectionelement 4, and a lead wire connection section 17 electrically connectedwith a lead wire 46.

The frame main body section 12 has nearly at an axially central positiona curved portion 13 and is configured so that a front end side portioncloser to the front end than the curved portion 13 and a rear end sideportion closer to the rear end than the curved portion 13 are differentin the position with respect the plate surface thickness direction. Thesurface of the curved portion 13, that faces the frame abutment portion15 constitutes an inclined surface that faces the front end side and hasa function of inhibiting the frame abutment portion 15 from movingaxially toward the rear end side or radially outward at the time ofabutting engagement with the frame abutment portion. Further, the framemain body section 12 is formed so as to be 1.1 mm in the width size W1and 0.2 mm in the thickness at the plate surface of the front end sideportion closer to the front end than the central position.

Herein, the “width size” is intended to indicate the size perpendicularto the axial direction and to the direction in which the elementabutment section 16 and the frame main body section 12 are spaced fromeach other. Further, the lead frames 10 (first lead frame 11 and secondlead frame 211) are formed so as to be smaller in the width size and inthe thickness as compared with the conventional lead frame.

The first lead frame 11 has a first frame locking section 19 that isformed able to be disposed in the first locking groove 90 of theseparator 82. The first frame locking section 19 is extended from a sidesurface of a front end side portion of the frame main body section 12 inthe direction perpendicular to the plate surface and bent so as to havea portion parallel with the plate surface of the frame main body section12. Namely, the first frame locking section 19 has a larger width (totalwidth) than the remaining portion of the frame main body section 12 whendeveloped so as to extend in the width direction of the remainingportion.

The first frame locking section 19 has a first extension portion 131extending from a side surface of a front end side portion of the framemain body section 12 in the direction perpendicular to the plate surfaceand a second extension portion 133 extending from an end of the firstextension portion 131, which is opposite to a connection side forconnection with the frame main body section 12, in parallel with theframe main body section 12. Of the extension portions, the firstextension portion 131 extends from the front end side portion of theframe main body section 12 in the direction apart from the elementabutment section 16.

The first extension portion 131 and the second extension portion 133 ofthe first frame locking section 19 have a first locking surface 135 thatfaces axially toward the rear end side, and the second extension portion133 has a second locking surface 137 that faces in the direction of anintervening space between the frame main body section 12 and the elementabutment section 16 and toward the element abutment section 16.

The element abutment section 16 is configured so as to extend whilebeing bent radially inward to change the direction of extension, from afront end of the frame main body section 12 axially toward the rear endside. The element abutment section 16 includes a connection side endportion 14 connected to the front end of the frame main body section 12and a frame abutment portion 15 that is positioned closer to the rearend than the connection side end portion 14 and put in a state of beingspaced apart from the frame main body section 12 when the first leadframe 11 itself is in a free state.

Herein, the element abutment section 16 is formed so as to be 1.1 mm inthe width side of the plate surface and 0.2 mm in the thickness.Further, element abutment section 16 is formed into a circular arc shapeand curved so that the distance between the axially central portion andthe frame main body section 12 is larger as compared with that betweenthe frame abutment portion 15 and the frame main body section 12 and aconvex side curved surface of the circular arc shape is abuttinglyengaged with the detection element 4.

In the meantime, when an external force is applied to the elementabutment section 16 (specifically, an external force from the elementabutment section 16 toward the frame main body section 12 is applied),the frame abutment portion 15 is resiliently deformed toward the framemain body section 12, and finally the frame abutment portion 15 isabuttingly engaged with the curved portion 13 of the frame main bodysection 12.

Further, the first lead frame 11 is configured so that when there is noexternal force applied thereto and the connection side end section 14(the element abutment section itself) is not resiliently deformed, thedistance between the abutment portion 15 of the element abutment section16 and the frame main body section 12 is smaller than the depth of thefirst frame disposition groove 86 and the second frame dispositiongroove 88 of the separator 82.

In the meantime, the first lead frame 11 is configured so that in casethe element abutment section 16 in a state of being resiliently deformedtoward the frame main body section 12 is held between the detectionelement 4 and the separator 82, the abutment portion 15 of the elementabutment section 16 is brought into contact with the curved portion 13of the frame main body section 12 and at least a portion of the elementabutment section 16 protrudes from the first frame disposition groove 86and the second frame disposition groove 88 to contact an electrodeterminal section of the detection element 4.

Then, the second lead frame 211 will be described.

The second lead frame main body section 212 is formed so that a frontend side portion closer to the front end than a portion around a curvedportion 213 is 0.8 mm in the plate surface width W2 and 0.2 mm in theplate thickness and substantially similar in the sectional shape withrespect to a plane parallel to the axial direction and perpendicular tothe plate surface, to the frame main body section 12 though different inthe width of a lateral surface from the frame main body section 12 ofthe first lead frame 11.

The second element abutment section 216 is formed so as to be 0.8 mm inthe plate surface width W2 and 0.2 mm in the plate thickness andsubstantially similar in the circular arc sectional shape with respectto a plane parallel to the axial direction, to the element abutmentsection 16, and has a second connection side end portion 214corresponding to the connection side end portion 14 and a second frameabutment portion 215 corresponding to the frame abutment portion 15.

Further, the second lead frame 211 has at a portion of the second framemain body section 212 two second frame locking sections 219 that can bedisposed in the second locking grooves 91 of the separator 82. Thesecond locking sections 219 are configured so as to extend from thesecond main body section 212 in the direction perpendicular to the platesurface thereof and be bent outward to have portions parallel to theplate surface of the second frame main body section 212 thereby beingnearly L-shaped in section. Namely, the second frame locking section219, when developed in the width direction of a remaining portion of thesecond frame main body section 212, has a wider width than that of theremaining portion.

The second locking section 219 has a third extension portion 231extending from the front end side portion of the second frame main bodysection 212 in the direction perpendicular to the plate surface thereofand a fourth extension portion 233 extending from the end of the thirdextension portion 231, which is positioned at the side opposite to theconnection side for connection with the second frame main body section212, in parallel with the second frame main body section 212. Of theextension portions, the third extension portion 231 extends from thefront end side portion of the second frame main body section 212 in thedirection of an intervening space between the second frame main bodysection 212 and the second element abutment section 216 and in thedirection apart from the second element abutment section 216. Further,the two second frame locking sections 219 are configured so that thefourth extension portions 233 extend in the opposite directions.

Of the second frame locking section, the third extension portion 231 andthe fourth extension portion 233 have a third locking surface 235 facingaxially toward the rear end side of the second frame main body section212, and the fourth extension portion 233 has a fourth locking surface237 facing the second element abutment section 216.

Further, the second lead frame 211 has a second lead wire connectionsection 217 which is formed into a similar shape to the lead wireconnection section 17 of the first lead frame 11 and in a manner as tobe connected to the rear end of the second lead frame main body section212.

Of the lead frames 10 configured in this manner, the four first leadframes 11 and one second lead frame 211 are inserted into the insertionhole 84 of the separator 82 so as to be put in a state of beinginsulated from each other by the first rib portions 87 and the secondrib portions 89. In this instance, the four first lead frames 11 aredisposed in the two first frame disposition grooves 86 corresponding tothe electrode terminal sections 30, 32 of the detection element 4 and inthe two frame disposition grooves 88 corresponding to the two secondframe disposition grooves 88 corresponding to the electrode terminalsections 34, 36. The second lead frame 211 is disposed in the firstframe disposition groove 86 corresponding to the electrode terminalsection 31 of the detection element 4.

FIG. 5 is a perspective view of the separator 82 insertion hole 84 inthe state in which the lead frame 10 is inserted into the insertion hole84.

As shown in FIG. 5, in case the first lead frame 11 is disposed in theinsertion hole 84, the first frame locking section 19 of the first leadframe 11 is disposed in the first locking groove 90 of the separator 82.As a result, the first locking surface 135 of the first frame lockingsection 19 (refer to FIG. 3) and the second locking surface 137 (referto FIG. 3) are put into a condition of being engaged with the inner wallsurface of the first locking groove 90.

Further, in case the second lead frame 211 is disposed in the insertionhole 84 of the second lead frame 211, the second frame locking section219 of the second lead frame 211 is disposed in the second lockinggroove 91 of the separator 82. As a result, the third locking surface235 of the second frame locking section 219 (refer to FIG. 3) and thefourth locking surface 237 (refer to FIG. 3) are put into a condition ofbeing engaged with the inner wall surface of the second locking groove91.

In the meantime, the lead frame 10 is disposed in the insertion hole 84through insertion into the insertion hole 84 of the separator togetherwith the lead wire 46 after the lead wire 46 is connected to the leadwire connection section 17 (second lead wire connection section 217).

By inserting the detection element 4 into the contact insertion hole 84of the separator 84 in a state of disposing therein the lead frames 10as described above, the element abutment sections 16 (second elementabutment sections 216) can be abuttingly engaged and electricallyconnected with the electrode terminal sections 30, 31, 32, 34, 36 of thedetection element 4.

Then, the assembly work for inserting the detection element 4 into theinsertion hole 84 in a state of disposing therein the lead frames 10thereby assembling the detecting element 4, the lead frame 10 and theseparator 82 into a unit will be described.

FIG. 6 illustrates the states of deformation of the lead frame 10 withinthe insertion hole 84 during the work for inserting the detectionelement 4 into the insertion hole 84 of the separator 82. In themeantime, in FIG. 6, one lead frame 10 and the detection element 4 areshown and the separator 82 is omitted for brevity.

First, at the first step immediately after the beginning of the assemblywork, the detection element 4 is disposed at the front end side of theseparator 82 and thereafter the detection element 4 is moved to thefront end side opening portion of the insertion hole 84 while at thesame time the detection element 4 is abuttingly engaged with the elementabutment section 16 of the lead frame 10.

Then, in the second step, the detection element 4 is pushed against theelement abutment section 16 of the lead frame 10 to apply thereto anexternal force thereby performing a work for resiliently deforming theportion around the connection side end portion 14 (namely, the elementabutment section 16 is resiliently deformed toward the frame main bodysection 12) and making the frame abutment portion 15 of the elementabutment section 16 go closer to the curved portion 13 of the frame mainbody section 12. Then, the detection element 4 is pushed against theelement abutment section 16 further thereby resiliently deforming theelement abutment section 16 against the frame main body section 12 andabuttingly engaging the frame abutment portion 15 of the elementabutment section 16 with the curved portion 13 of the frame main bodysection 12. By this, the element abutment section 16 is put into a stateof being supported at two places, i.e., at the connection side endportion 14 and the frame abutment portion 15, i.e., put into a two-pointsupport condition.

At the next third step, a work for inserting the detection element 4further into the rear end side of the insertion hole 84 and changing therelative positions of the detection element 4 and the separator 82 isperformed. By this, the front end side portion of the frame main bodysection 12 and the element abutment section 16 of the lead frame 10 areput into the condition of being placed between the detection element 4and the inner wall surface of the insertion hole 84 (refer to FIG. 1).In this instance, the element abutment section 16 is resilientlydeformed so as to allow the axially central portion thereof to extendalong the plate surface of the detection element 4 and therefore putinto a condition of being abuttingly engaged at a wide area with theelectrode terminal section of the detection element 4.

By performing the assembly work in the above-described manner, thedetection element 4, the lead frame 10 and the separator 82 can beassembled into a unit. While the resilient deformation states of thefirst lead frame 11 at the time of assembly work have been hereindescribed, the second lead frame 211 exhibits the similar deformationstates to the first lead frame 11.

In the meantime, at the time of insertion of the detection element 4into the insertion hole 84, an external force is applied to the leadframe 10 in the direction to cause the frame main body section 12 apartfrom the inner wall surface of the insertion hole 84 due to thefrictional force caused between the detection element 4 and the leadframe 10 (specifically, the element abutment section 16).

In contrast to this, the first lead frame 11 of the lead frames 10 isdisposed in the insertion hole 84 in a way as to cause the first lockingsurface 135 and the second locking surface 137 of the first framelocking section 19 to engage the inner wall surface of the first lockinggroove 90. Further, the second lead frame 211 of the lead frames 10 isdisposed in the insertion hole 84 so as to be put in a state where thethird locking surface 235 and the fourth locking surface 237 of thesecond locking section 219 are engaged with the inner wall surface ofthe second locking groove 91.

By engagement of the first locking surface 135 of the first framelocking section 19 with the inner wall surface of the first lockinggroove 90, it becomes possible to inhibit the frame main body section 12from moving axially toward the rear end side. Further, by engagement ofthe second locking surface 137 of the first frame locking section 19with the inner wall surface of the first locking groove 90, it becomespossible to inhibit the frame main body section 12 from moving in thedirection apart from the inner surface of the insertion hole 84.Similarly, by engagement of the third locking surface 235 of the secondframe locking section 219 with the inner wall surface of the secondlocking groove 91, it becomes possible to inhibit the second frame mainbody section 212 from moving axially toward the rear end side. Further,by engagement of the fourth locking surface 237 of the second framelocking section 219 with the inner wall surface of the second lockinggroove 91, it becomes possible to inhibit the second frame main bodysection 212 from moving in the direction apart from the inner surface ofthe insertion hole 84.

Namely, movement of the frame main body section 12 (the second framelocking section 219) can be inhibited even in case an external force isapplied to the lead frame 10, thus making it possible to prevent therelative positions of the lead frame 10 (first lead frame 11, secondlead frame 211) and the detection element 4 from being varied.

In the meantime, the assembly work for assembling the detection element4, the lead frame 10 and the separator 82 into an integral unit isexecuted in the middle of a production process of the air/fuel ratiosensor 2. In the production process of the air/fuel ratio sensor 2, itis executed in the stage prior to the assembly work, a work forassembling an intermediate assembly part consisting of the detectionelement 4, the ceramic sleeve 6, the talcum ring 108, the ceramic holder106, the metallic housing 102, etc. FIG. 7 is a perspective view of theintermediate assembly part 105 in a state where the rear end side of thedetection element 4 protrudes from the rear end portion 104 of themetallic housing 102 and the rear end portion of the ceramic sleeve 6.

In the production process of the air/fuel ratio sensor 2, the lead frame10 and the separator 82 can be attached to the detection element 4 byperforming the above-described assembly work on the detection element 4in the state of constituting the intermediate assembly part 105.

By executing, after the separator 82 and the detection element areassembled together, a fixing work, etc. for joining the outer tube 4,etc. to the metallic housing 102 by laser welding or the like and fixingthe grommet 50 to the outer tube 44 by caulking, the air/fuel ratiosensor 2 is completed and the production process of the air/fuel ratiosensor 2 is finished.

In the meantime, in this embodiment, the lead frame 10 corresponds tothe metallic terminal member described in “what is claimed is” and theinsertion hole 84 corresponds to the element insertion hole. Of thesecond lead frame 211, the third locking surface 235 of the second framelocking section 219 corresponds to the first locking surface describedin “what is claimed is”, and the fourth locking surface 237 correspondsto the second locking surface described in “what is claimed is”.

Further, of the sensor production process, the working step fordisposing the lead frame 10 within the contact insertion hole 84 of theseparator 82, disposing the first frame locking section 19 in the firstlocking groove 90 and disposing the second frame locking section 219 inthe second locking groove 91 corresponds to the first step described in“what is claimed is”, and the first step in the assembly work forassembling the detection element 4, the lead frame 10 and the insulationcontact member 82 together corresponds to the second step described in“what is claimed is”. Further, the second step and the third step in theassembly work for assembling the detection element 4, the lead frame 10and the insulation contact member 82 together corresponds to the thirdstep described in “what is claimed is”.

As having been described above, the air/fuel ratio sensor 2 of thisembodiment is configured to include the lead frame 10 having the framemain body section 12 and the element abutment section 16, and the leadframe 10 is configured so as to constitute part of a current path byabuttingly engaging the element abutment sections 16 with the electrodeterminal sections 20, 31, 32, 34, 36 of the detection element by theeffect of a restoring force caused by resilient deformation of theelement abutment section 16 toward the frame main body section 12.

Of the lead frames 10, the first lead frame 11 includes the first framelocking section 19 having the first locking surface 135 and the secondlocking surface 137 and is configured so that the first frame lockingsection 19 is disposed in the first locking groove 90 of the separator82 and the first locking surface 135 and the second locking surface 137engage the inner wall surface of the first locking groove 90. Further,of the lead frames 10, the second lead frame 211 includes the secondframe locking section 219 having the third locking surface 235 and thefourth locking surface 237 and is configured so that the second framelocking section 219 is disposed in the second locking groove 91 of theseparator 82 and the third locking surface 235 and the fourth lockingsurface 237 engage the inner wall surface of the second locking groove91.

In the first lead frame 11, movement of the frame main body section 12axially toward the rear end side can be inhibited by engagement of thefirst locking surface 135 of the first frame locking section 19 with theinner wall surface of the first locking groove 90, and movement of theframe main body section 12 in the direction apart from the inner surfaceof the insertion hole 84 of the frame main body section 12 can beinhibited by engagement of the second locking surface 137 of the firstframe locking section 19 with the inner wall surface of the firstlocking groove 90. Further, in the second lead frame 211, movement ofthe second frame main body section 212 axially toward the rear end sidecan be inhibited by engagement of the third locking surface 235 of thesecond frame locking section 219 with the inner wall surface of thesecond locking groove 91, and movement of the second main body section212 in the direction apart from the inner surface of the insertion hole84 can be inhibited by engagement of the fourth locking surface 237 ofthe second frame locking section 219 with the inner wall surface of thesecond locking groove 91.

Namely, movement of the frame main body section 12 (second frame mainbody section 212) can be inhibited even in the case an external force isapplied to the lead frame 10, thus making it possible to prevent therelative positions of the lead frame 10 and the detection element 4 frombeing varied.

Accordingly, by this embodiment, a variation in the relative positionsof the lead frame 10 and the detection element 4 can be prevented evenin the case an inadequate external force is applied to the lead frame10, and the electrical connection of the lead frame 10 with theelectrode terminal sections 30, 31, 32, 34, 36 can be maintainedsuitably.

As a result, at the time of the assembly work of assembling thedetection element 4, the lead frame 10 and the separator 82 together,buckling of the lead frame 10 is hard to be caused, therefore thefrequency at which a defective is caused in the sensor production workcan be decreased, and the sensor production efficiency can be improved.

Further, the air/fuel ratio sensor 2 of this embodiment is constructedto use the lead frame 10 (first lead frame 11, second lead frame 211)which is configured so that the support condition of the elementabutment section 16 which is brought into contact with the electrodeterminal section of the detection element 4 varies from the one-pointsupport condition to the two-point support condition.

The lead frame 10 in a state where the frame abutment portion 15 (secondframe abutment portion 215) of the element abutment section 16 is notengaged with the frame main body section 12 (second frame main bodysection 212), i.e., in the one-point support condition is configured soas to push the element abutment section 16 against the electrodeterminal section of the detection element 4 with a small stress causedby resilient deformation of the connection side end portion 14 (secondconnection side end portion 214) and its adjacent portion. Further, incase the frame abutment portion 15 (second frame abutment portion 215)is abuttingly engaged with the frame main body section 12 (second framemain body section 212), the lead frame 10 produces a large stress due toresilient deformation of the axially central portion of the elementabutment section 16 (second element abutment section 216).

Namely, the lead frame 10 is configured to produce a larger pressure forpressing the element abutment section 16 (second element abutmentsection 216) against the detection element 4 when in the two-pointsupport condition where the frame abutment portion 15 (second frameabutment portion 215) of the element abutment section 16 (second elementabutment section 216) is abuttingly engaged with the frame main bodysection 12 (second frame main body section 212) than when in theone-point support condition where the frame abutment portion 15 (secondframe abutment portion 215) of the element abutment section 16 (secondelement abutment section 216) is not abuttingly engaged with the framemain body section 12 (second frame main body section 212).

By this, at the time of assembling the lead frames 10 and the detectionelement 4 together in the production process of the air/fuel ratiosensor 2, the element abutment sections 16 (second element abutmentsections 216) of the lead frames 10 are pressed against the electrodeterminal sections 30, 31, 32, 34, 36 with a relatively smaller force inthe first half stage of the assembly work. As a result, at the time ofthe assembly work for assembling the lead frames 10 and the detectionelement 4, it becomes possible to prevent an excessively large pressurefrom being caused by resilient deformation of the lead frame 10 andapplied to the detection element 4, and it becomes possible to inhibitthe detection element 4 from being broken by application of pressure.

Further, after the assembly work is completed, the element abutmentsection 16 (second element abutment section 216) is brought into thetwo-point support condition of being supported at the connection sideend portion 14 (second connection side end portion 214) and the frameabutment portion 15 (second frame abutment portion 215) upon the framemain body section 12 (second frame main body section 212). By a largestress (resilient force) caused by resilient deformation of the elementabutment section 16 (second element abutment section 216) in thetwo-point support condition, the element abutment section 16 (secondelement abutment section 216) itself of the lead frame 10 is pressedagainst the electrode terminal section of the detection element 4, thusmaking good the condition of electrical connection between the leadframe 10 and the detection element 4.

For this reason, it is unnecessary to make the lead frame 10 larger inthe width and thickness for the purpose of attaining a large resilientforce and thereby making good the condition of connection between thelead frame 10 and the detection element 4. Namely, as compared with alead frame having an element abutment section in a one-point supportcondition, the lead frame 10 of this embodiment has an advantage ofbeing able to be smaller in the width and thickness for producing anequal resilient force.

While the embodiment of this invention has been described as above, theinvention is not limited to the above-described embodiment (hereinafteralso referred to as the first embodiment) but can be of various otherembodiments.

Then, a second wide-range air/fuel ratio sensor (hereinafter alsoreferred to as a second air/fuel ratio sensor) with a lead frame havinga wide protrusion portion that protrudes in the width directionaccording to the second embodiment will be described.

In the meantime, since the second air/fuel ratio sensor is differentfrom the air/fuel ratio sensor 2 of the first embodiment in that a leadframe and separator are formed into different shapes but other members(metallic housing member, detection element, etc.) are similar in shape,description will hereinafter be made mainly to the lead frame and theseparator.

The second air/fuel ratio sensor includes a third lead frame 251, afourth lead frame 253 and a second separator 182.

First, the second separator 182 will be described.

In FIG. 8 is shown a perspective view of an external appearance of thesecond separator 182 when observed from the front end side thereof. Inthe meantime, in FIG. 8, the second separator 182 in the state where thethird lead frame 251 and the fourth lead frame 253 are disposed in asecond insertion hole 184 is shown in a perspective view.

As shown in FIG. 8, the second separator 182 is formed into a tubularshape having the second insertion hole 184 extending axiallytherethrough and has a second flange portion 183 protruding axiallyoutward from an external surface thereof. The second separator 182 isabuttingly engaged at the second flange portion 183 with the outer tubeside support portion 64 of the outer tube 44 and thereby disposed insidethe outer tube 44. In the meantime, the outer tube side support portion64 is formed so as to protrude inward of the outer tube 44.

At the inner wall surface of the second insertion hole 184, which facesthe first plate surface 21 of the detection element 4 (refer to FIG. 1)are formed two first rib portions 187 that protrude inward. The firstrib portions 187 are provided to serve as lead frame boundary portionsinside the insertion hole for forming boundaries of three narrow framedisposition grooves 186 for disposing three fourth lead frames 253separately and in a state of being electrically insulated from eachother. The three narrow frame disposition grooves 186 are formed at thepositions corresponding to the electrode terminal sections 30, 31 and 32at the first plate surface 21 of the detection element 4.

Further, at the inner wall surface of the second insertion hole 184,which faces the second plate surface 23 of the detection element 4(refer to FIG. 1), is formed one second rib portion 189 that protrudesinward. The second rib portion 189 is provided to serve as a lead frameboundary portion inside the insertion hole for forming a boundary of twowide frame disposition holes 188 for disposing two third lead frames 251separately and in a state of being electrically insulated from eachother. The two wide frame disposition grooves 188 are formed at thepositions corresponding to the electrode terminal sections 34, 36 at thesecond plate surface 23 of the detection element 4.

The first rib portion 187 and the second rib portion 189 have a functionof preventing the lead frames disposed in the adjacent frame dispositiongrooves from contacting each other and can prevent the adjacent leadframes from being electrically connected to each other and therebyprevent the electrical path from being deteriorated.

Further, the second separator 182 has at the front end surface (thisside surface in the figure) wide locking grooves 190 and narrow lockinggrooves 191 that are joined to the front end side opening portion of thesecond insertion hole 184.

The wide locking groove 190 is formed so as to have a nearly L-shapedsection with respect to a plane perpendicular to the axial direction andso as to dispose therein a first wide connection portion 271 and asecond wide connection portion 273 of the third lead frame 251, whichwill be described later. In the meantime, the wide locking grooves 190are formed at two portions joined to the two wide locking grooves 190.

The narrow locking groove 191 is formed so as to have a nearly L-shapedsection with respect to a plane perpendicular to the axial direction andso as to dispose therein a first narrow connection portion 321 and asecond narrow connection portion 323 of the fourth lead frame 253, whichwill be described later. In the meantime, the narrow locking grooves 191are formed at three portions joined to the three narrow framedisposition grooves 186.

Then, the third lead frame 251 and the fourth lead frame 253 will bedescribed.

FIG. 9 is a perspective view showing external appearances of the thirdlead frame 251 and the fourth lead frame 253.

The third lead frame 251 includes a third frame main body section 262formed from a long, axially extending plate and a third element abutmentsection 266 extending so that at least a portion thereof is disposedbetween the third frame main body section 262 and the detection element4, and is configured so that the third element abutment section 266(specifically, a portion of the third element abutment section 266) isabuttingly engaged with an electrode terminal section of the detectionelement 4.

The third frame main body section 262 includes a third curved portion263 at a nearly axially central position and is configured so that afront end side portion positioned closer to the front end than the thirdcurved portion 263 and a rear end side portion positioned closer to therear end than the third curved portion 263 are different in the positionwith respect to the plate surface thickness direction. Further, thethird frame main body section 262 is formed so as to be 1.2 mm in theplate surface width size W3 and 0.2 mm in the thickness.

Herein, the term “width size” is herein used to indicate the size in thedirection perpendicular both to the axial direction and to the directionin which the third element abutment section 266 and the third frame mainbody section 262 are spaced from each other. Further, the third leadframe 251 is smaller in the width size and in the thickness as comparedwith the conventional lead frame.

A wide connection section 264 constituting part of the third frame mainbody section 262 of the third lead frame 251 is configured to include afirst wide connection portion 271 and a second wide connection portion273 and further include a wide protrusion portion 231 that protrudesfrom one side surface of the second wide connection portion 273 in thewidth direction of the second wide connection portion 273. In themeantime, the front end of the second wide connection portion 273 isconnected to a third connection side end portion 275 of the thirdelement abutment section 266.

The first wide connection portion 271 extends from a front end sideportion of the third frame main body section 262 in the direction of anintervening space between the third frame main body section 262 and thethird element abutment section 266 and in the direction apart from thethird element abutment section 266.

The second wide connection portion 273 extends from the end of the firstwide connection portion 271 on the side remoter from the third elementabutment section 216, axially toward the front end of the third framemain body section 262.

The first wide connection portion 271 of the third lead frame 251 has afist locking surface 283 that faces axially toward the rear end side ofthe third lead frame 251. Further, the wide protrusion portion 281 ofthe third lead frame 251 has a second locking surface 285 facing in thedirection of an intervening space between the third frame main bodysection 262 and the third element abutment section 266 and toward thethird element abutment section 266 (detection element 4).

Namely, the wide connection section 264 is configured to have the firstlocking surface 283 and the second locking surface 285 and correspondsto the frame locking section described in “what is claimed is”.

The third element abutment section 266 is configured so that when thethird lead frame 251 itself is in a free state, a third frame abutmentportion 265 that is an axial rear end portion of the third elementabutment section 266 is put in a state of being spaced apart from thethird frame main body section 262. Further, the third element abutmentsection 266 is formed into a circular arc shape which is so curved as toallow the space between the axially central portion thereof and thethird frame main body section 262 to be larger as compared with thespace between the third frame abutment portion 265 and the third framemain body section 262 and to allow the convex side surface of thecircular arc shape to an electrode terminal section of the detectionelement 4.

In the meantime, the third element abutment section 266 is configured toresiliently deform at the third connection side end portion 27 and aportion adjacent thereto and continue resilient deformation toward thethird frame main body section 262 thereby allowing the third frameabutment portion 265 to abuttingly engage the third frame main bodysection 262.

Further, the third lead frame 251 is configured so that when there is noexternal force applied thereto and the third element abutment section266 is not resiliently deformed (when in a free state), the spacebetween the third frame abutment portion 265 of the third elementabutment section 266 and the third main body section 262 is smaller thanthe depth size of the wide frame disposition groove 188 of the secondseparator 182.

In the meantime, the third lead frame 251 is configured so that when thethird element abutment section 266 is placed between the detectionelement 4 and the second separator 182 and resiliently deformed towardthe third frame main body section 262, the third frame abutment portion265 of the third element abutment section 266 is abuttingly engaged withthe third frame main body section 262 and at least a portion of thethird element abutment section 266 is disposed outside the wide framedisposition groove 188 to abuttingly engage an electrode terminalsection of the detection element 4.

Further, the third lead frame 251 has a third lead wire connectionsection 267 connected to a rear end (upper end portion in the figure) ofthe third frame main body section 262. The third lead wire connectionsection 267 is formed into a nearly tubular shape by bending and thencaulked radially inward under a condition of having a core line of thelead wire 46 (not shown) inserted thereinto thereby being electricallyconnected to the lead wire 46. In the meantime, FIG. 9 shows the thirdlead wire connection section 267 in a state of being formed into anearly tubular shape.

Then, the fourth lead frame 253 includes a fourth frame main bodysection 312 formed from a long, axially extending plate and a fourthelement abutment section 316 extending so that at least a portionthereof is disposed between the fourth frame main body section 312 andthe detection element 4, and is configured so that the fourth elementabutment section 316 (specifically, a portion of the fourth elementabutment section 316) abuttingly engages an electrode terminal sectionof the detection element 4.

The fourth frame main body section 312 includes a fourth curved portion313 at an axially nearly central position and is configured so that afront end side portion positioned closer to the front end than thefourth curved portion 313 and a rear end side portion positioned closerto the rear end than the fourth curved portion 313 are different in theposition with respect to the plate surface thickness direction. Further,the fourth frame main body section 312 is formed so as to be 0.8 mm inthe plate surface width size W4 and 0.2 mm in the thickness.

Herein, the term “width size” is herein used to indicate the size in thedirection perpendicular both to the axial direction and to the directionof an intervening space between the fourth element abutment section 316and the fourth frame main body section 312. Further, the fourth leadframe 253 is smaller in the width size and in the thickness as comparedwith the conventional lead frame.

A narrow connection section 314 of the fourth lead frame 253 isconfigured to include a first narrow connection portion 321 and a secondnarrow connection portion 323 and further include a wide protrusionportion 331 that protrudes from the side surface of the second narrowconnection portion 323 in the width direction of the second narrowconnection portion 323. In the meantime, the front end of the secondnarrow connection portion 273 is connected to a fourth connection sideend portion 325 of the fourth element abutment section 316.

The first narrow connection portion 321 extends from the front end sideportion of the fourth frame main body section 312 in the direction of anintervening space between the fourth frame main body section 312 and thefourth element abutment section 316 and in the direction apart from thefourth element abutment section 316.

The second narrow connection portion 323 extends from the end of thefirst narrow connection portion 321, which is on the side remoter fromthe fourth element abutment section 316, axially toward the front end ofthe fourth frame main body section 312.

The first narrow connection portion 321 of the fourth lead frame 253 hasa fist locking surface 333 that faces axially toward the rear end sideof the fourth lead frame main body section 312. Further, the second wideprotrusion portion 331 of the fourth lead frame 253 has a second lockingsurface 335 that faces in the direction of an intervening space betweenthe fourth frame main body section 312 and the fourth element abutmentsection 316 and toward the fourth element abutment section 316(detection element 4 side).

Namely, the narrow connection section 314 is configured to have thefirst locking surface 333 and the second locking surface 335 andcorresponds to the frame locking section described in “what is claimedis”.

The fourth element abutment section 316 is configured so that when thefourth lead frame 253 itself is in a free state, the fourth frameabutment portion 315 that is an axially rear end portion of the fourthelement abutment section 316 is in a state of being spaced apart fromthe fourth frame main body section 312. Further, the fourth elementabutment section 316 is formed into a circular arc shape which is socurved as to allow the space between the axially central portion thereofand the fourth frame main body section 312 to be larger as compared withthe space between the fourth frame abutment portion 315 and the fourthframe main body section 231 and to allow the convex side surface of thecircular arc shape to abuttingly engage an electrode terminal section ofthe detection element 4.

In the meantime, the fourth element abutment section 316 is configuredto resiliently deform at the third connection side end portion and aportion adjacent thereto and continue resilient deformation toward thefourth frame main body section 312 for thereby allowing the fourth frameabutment portion 315 to abuttingly engage the fourth frame main bodysection 312.

Further, the fourth lead frame 253 is configured so that when there isno external force applied to the fourth lead frame and the fourthelement abutment section 316 is not resiliently deformed (when in a freecondition), the space between the fourth frame abutment portion 315 ofthe fourth element abutment section 316 and the fourth frame main bodysection 312 is smaller than the depth size of the narrow framedisposition groove 186 of the second separator 182.

In the meantime, the fourth lead frame 253 is configured so that whenplaced between the detection element 4 and the second separator 182 toallow the fourth element abutment section 316 to resiliently deformtoward the fourth frame main body section 312, the fourth frame abutmentportion 315 of the fourth element abutment section 316 is abuttinglyengaged with the fourth frame main body section 312 and at least aportion of the fourth element abutment section 316 is disposed outsidethe narrow frame disposition groove 186 to abuttingly engage anelectrode terminal section of the detection element 4.

Further, the fourth lead frame 253 has a fourth lead wire connectionsection 317 connected to a rear end (upper end portion in the figure) ofthe fourth frame main body section 312. The fourth lead wire connectionsection 317 is formed into a nearly tubular shape by bending and thencaulked radially inward under a condition of having a core line of thelead wire 46 inserted thereinto thereby being electrically connected tothe lead wire 46 (not shown). In the meantime, FIG. 9 shows the fourthlead wire connection section 317 in a state of being formed into anearly tubular shape.

As shown in FIG. 8, in case the third lead frame 251 is disposed in thesecond insertion hole 184, the first wide connection portion 271 and thewide protrusion portion 281 of the third lead frame 251 are disposed inthe wide locking groove 190 of the second separator 182. As a result,the first locking surface 283 of the first wide connection portion 271and the second locking surface 285 of the wide protrusion portion 281are put into a condition of being engaged with the inner wall surface ofthe wide locking groove 190.

Further, in case the fourth lead frame 251 is disposed in the secondinsertion hole 184, the first narrow connection portion 321 and thesecond wide protrusion portion 331 of the fourth lead frame 253 aredisposed in the narrow locking groove 191 of the second separator 182.As a result, the first locking surface 333 of the first narrowconnection portion 321 and the second locking surface 335 of the secondwide protrusion portion 331 are put into a condition of being engagedwith the inner wall surface of the narrow locking groove 191.

In the meantime, the third lead frame 251 is disposed in the secondinsertion hole 184 through insertion into the second insertion hole 184of the second separator 182 together with the lead wire 46 after thelead wire 46 is connected to the third lead wire connection section 267(second lead wire connection section 217). Further, the fourth leadframe 253 is disposed in the second insertion hole 184 through insertioninto the second insertion hole 184 of the second separator 182 togetherwith the lead wire 46 after the fourth lead wire connection section 317is connected with the lead wire 46.

By inserting the detection element 4 into the contact insertion hole 184of the second separator 182 in a state of disposing therein the thirdlead frames 251 and the fourth lead frames 253 in the above-describedmanner, the third element abutment sections 266 of the third lead frames251 can be electrically connected to the electrode terminal sections 34,36 of the detection element 4 and the fourth element abutment sections316 of the fourth lead frames 253 can be electrically connected to theelectrode terminal sections 30, 31, 32.

In the meantime, in the second embodiment, the third lead frame 251 andthe fourth lead frame 253 correspond to the metallic terminal membersdescribed in “what is claimed is”, and the second insertion hole 184corresponds to the insertion hole. Further, of the third lead frame 251,the first locking surface 283 of the first wide connection portion 271corresponds to the first locking surface described in “what is claimedis” and the second locking surface 285 of the wide protrusion portion281 corresponds to the second locking surface described in “what isclaimed is”. Further, of the fourth lead frame 253, the first lockingsurface 333 of the first narrow connection portion 321 corresponds tothe first locking surface described in “what is claimed is” and thesecond locking surface 335 of the second wide protrusion portion 331corresponds to the second locking surface described in “what is claimedis”.

Further, the first wide connection portion 271 and the first narrowconnection portion 321 correspond to the first connection portionsdescribed in “what is claimed is”, the second wide connection portion273 and the second narrow connection portion 323 correspond to thesecond connection portions, and the wide protrusion portion 281 and thesecond wide protrusion portion 331 correspond to the wide protrusionportion.

As having been described above, the second air/fuel ratio sensoraccording to the second embodiment has the third lead frame 251 with thefirst locking surface 283 and the second locking surface 285 and isconfigures so that the first locking surface 283 and the second lockingsurface 285 are abuttingly engaged with the inner wall surface of thewide locking groove 190.

By such engagement of the first locking surface 283 of the third leadframe 251 with the inner wall surface of the wide locking groove 190, itbecomes possible to inhibit the third frame main body section 262 frommoving axially toward the rear end side. Further, by engagement of thesecond locking surface 285 with the inner wall surface of the widelocking groove 190, it becomes possible to inhibit the third frame mainbody section 262 from moving in the direction apart from the innersurface of the second insertion hole 184.

Further, the fourth lead frame 253 has the first locking surface 333 andthe second locking surface 335, and the first locking surface 333 andthe second locking surface 335 are abuttingly engaged with the innerwall surface of the narrow locking groove 191.

By such engagement of the first locking surface 333 of the fourth leadframe 253 with the inner wall surface of the narrow locking groove 191,it becomes possible to inhibit the fourth frame main body section 312from moving axially toward the rear end side. Further, by engagement ofthe second locking surface 335 with the inner wall surface of the narrowlocking groove 191, it becomes possible to inhibit the fourth frame mainbody section 312 from moving in the direction apart from the innersurface of the second insertion hole 184.

Namely, movement of the third frame main body section 262 and the fourthframe main body section 312 can be inhibited even in case an externalforce is applied to the third lead frame 251 and the fourth lead frame253, thus making it possible to prevent the relative positions of thethird lead frame 251 and the detection element 4 and the relativepositions of the fourth lead frame 253 and the detection element 4 frombeing varied.

Accordingly, by the second embodiment, a variation in the relativepositions of the lead frame and the detection element 4 can be preventedeven in case an inadequate external force is applied to the lead framesat the time of use of the third lead frame 251 and the fourth lead frame253 which are formed small in the width size and in the thickness, andthe electrical connection of the lead frames with the electrode terminalsections 30, 31, 32, 34, 36 can be maintained suitably.

As a result, at the time of the assembly work of assembling thedetection element 4, the lead frames and the separator 182 together,buckling of the lead frames is hard to be caused, therefore thefrequency at which a defective is caused in the sensor production workcan be decreased, and the sensor production efficiency can be improved.

Further, the fourth lead frame 253 does not have the second wideprotrusion portion 331 at each side of the second narrow connectionportion 323 but at one side surface of the second narrow connectionportion 323. This makes it possible to prevent a part of the first ribportion 187 of the second separator, in which the second wide protrusionportion 331 is disposed, from becoming too thin, thus enabling thesecond separator 182 to have such structure that is hard to break.

In brief, in case the second protrusion portions 331 are provided to theboth side surfaces of the second narrow connection portion 323, thefirst rib portion 187 needs to be formed thin in order to obtain thedisposition areas (narrow locking grooves 191) for disposition of therespective second wide protrusions 331 of the two adjacently disposedfourth lead frames 253.

In contrast to this, by using the fourth lead frame 253 in which thesecond wide protrusion 331 is provided to only one side surface of thenarrow connection portion 323, it becomes possible to prevent the firstrib portion 187 from becoming too thin at a portion thereof and obtain asensor with the second separator 182 being hard to break.

Then, a third wide-range air/fuel ratio sensor (hereinafter alsoreferred to as a second air/fuel ratio sensor) with a lead frame havinga wide protrusion portion that protrudes in the width directionaccording to the third embodiment will be described.

In the meantime, since the third air/fuel ratio sensor is different fromthe air/fuel ratio sensor 2 of the first embodiment in that a lead frameand separator are formed into different shapes but other members(metallic housing member, detection element, etc.) are similar in shape,description will hereinafter be made mainly to the lead frame and theseparator.

The third air/fuel ratio sensor includes a fifth lead frame 351, a sixthlead frame 353 and a third separator 282.

First, the third separator 282 will be described.

In FIG. 10 is shown a perspective view of an external appearance of thethird separator 282 when observed from the front end side thereof. Inthe meantime, in FIG. 10, the third separator 282 in the state where thefifth lead frame 351 and the sixth lead frame 353 are disposed in athird insertion hole 284 is shown in a perspective view.

As shown in FIG. 10, the third separator 282 is formed into a tubularshape having the third insertion hole 284 extending axially therethroughand has a third flange portion 280 protruding axially outward from anexternal surface thereof. The third separator 282 is abuttingly engagedat the third flange portion 280 with the outer tube side support portion64 of the outer tube 44 and thereby disposed inside the outer tube 44.In the meantime, the outer tube side support portion 64 is formed so asto protrude inward of the outer tube 44 (refer to FIG. 1).

At the inner wall surface of the third insertion hole 284, which facesthe first plate surface 21 (not shown) of the detection element 4 areformed two first rib portions 287 that protrude inward. The first ribportions 287 are provided to serve as lead frame boundary portionsinside the insertion hole for forming boundaries of three narrow framedisposition grooves 286 for disposing two fifth lead frames 353 and onesixth lead frame 353 separately and in a state of being electricallyinsulated from each other. The three narrow frame disposition grooves286 are formed at the positions corresponding to the electrode terminalsections 30, 31 and 32 at the first plate surface 21 of the detectionelement 4.

Further, at the inner wall surface of the third insertion hole 284,which faces the second plate surface 23 of the detection element 4 (notshown), is formed one second rib portion 289 that protrudes inward. Thesecond rib portion 289 is provided to serve as a lead frame boundaryportion inside the insertion hole for forming a boundary of two wideframe disposition grooves 288 for disposing two fifth lead frames 351separately and in a state of being electrically insulated from eachother. The two wide frame disposition grooves 288 are formed at thepositions corresponding to the electrode terminal sections 34, 36 at thesecond plate surface 23 of the detection element 4.

The first rib portion 287 and the second rib portion 289 have a functionof preventing the lead frames disposed in the adjacent frame dispositiongrooves from contacting each other and can prevent the adjacent leadframes from being electrically connected to each other and therebyprevent the electrical path from being deteriorated.

Further, the third separator 282 has at the front end surface (this sidesurface in the figure) third wide locking grooves 290 and third narrowlocking grooves 291 that are joined to the front end side openingportion of the third insertion hole 284.

The third wide locking groove 290 is formed so as to have a nearlyT-shaped section with respect to a plane perpendicular to the axialdirection and be capable of disposing therein a first wide connectionportion 271 and a second wide connection portion 273 of the fifth leadframe 351, which will be described later.

The third narrow locking groove 291 has a radial groove portion that isformed to extend from the front end side opening portion of the thirdinsertion hole 284 radially outward of the third separator 282. Further,the third narrow locking 291 is formed so as to be capable of disposingtherein a first narrow frame connection portion 421 and a second narrowframe connection potion 423 of the sixth lead frame 353, which will bedescribed later. In the meantime, the third narrow locking groove 291 isformed at a portion connected to central one of the three narrow framedisposition grooves 286 that are arranged side by side.

Then, the fifth lead frame 351 and the sixth lead frame 353 will bedescribed. FIG. 11 is a perspective view showing external appearances ofthe fifth lead frame 351 and the sixth lead frame 353.

The fifth lead frame 351 is constituted by adding a wide protrusion tothe third lead frame 251. Namely, the fifth lead frame 351 is configuredto include a wide protrusion portion 281 protruding from one sidesurface of the second wide connection portion 273 in the width directionof the second wide connection portion 273 and a third wide protrusionportion 381 protruding from the other side surface of the second wideconnection portion 273 in the width direction of the second wideconnection portion 273.

In the figure, the portions common to the fifth lead frame 351 and thethird lead frame 251 are designated by the same reference characters asthe third lead frame 251.

The fifth lead frame 351 is configured to include a fourth wideconnection section 364, and the fourth wide connection section 364 isconfigured to include a first wide connection portion 271, a second wideconnection portion 273, the wide protrusion portion 281 and the thirdwide protrusion portion 381. In the meantime, the front end of thesecond wide connection portion 273 is connected to the third connectionside end portion 275 of the third element abutment section 266.

Further, the third wide protrusion portion 381 of the fifth lead frame351 has a fifth locking surface 385 that faces in the direction of anintervening space between the third frame main body section 262 and thethird element abutment section 266 and toward the third element abutmentsection 266 side.

Namely, the fourth wide connection section 364 is configured to includea first locking surface 283, a second locking surface 285 and the fifthlocking surface 385 and corresponds to the frame locking sectiondescribed in “what is claimed is”.

Then, the sixth lead frame 353 includes a sixth frame main body section412 formed from a long, axially extending plate and a sixth elementabutment section 416 extending so that at least a portion thereof isdisposed between the sixth frame main body section 412 and the detectionelement 4, and is configured so that the sixth element abutment section416 (specifically, a portion of the sixth element abutment section 416)is abuttingly engaged with an electrode terminal section of thedetection element 4.

The sixth frame main body section 412 includes a sixth curved portion413 at a nearly axially central position and is configured so that afront end side portion positioned closer to the front end than the sixthcurved portion 413 and a rear end side portion positioned closer to therear end than the sixth curved portion 413 are different in the positionwith respect to the plate surface thickness direction.

The narrow frame connection section 414 of the sixth lead frame 353 isconfigured to include a first narrow frame connection portion 421 and asecond narrow connection portion 413 and a third narrow frame connectionportion 425.

The first narrow frame connection portion 421 extends from the front endside portion of the sixth frame main body section 412 in the directionof an intervening space between the sixth frame main body section 412and the sixth element abutment section 416 and in the direction apartfrom the sixth element abutment section 416.

The second narrow frame connection portion 423 extends from the endportion of the first narrow frame connection portion 421 on the sideremoter from the sixth element abutment section 416, axially toward therear end side of the sixth frame main body section 412.

The third narrow frame connection portion 425 is extended from the endportion of the second narrow frame connection portion 423 on the sideopposite to the connection side for connection with the first narrowframe connection portion 421, bent axially toward the front end side ofthe sixth frame main body section 412 and connected at a portion closerto the front end than the first narrow frame connection portion 421.

The first narrow frame connection portion 421 has a first lockingsurface 433 that faces axially toward the rear end side of the sixthframe main body section 412. Further, the second narrow frame connectionportion 423 has a second locking surface 435 that faces in the directionof an intervening space between the sixth frame main body section 412and the sixth element abutment section 416 and toward the sixth elementabutment section 416.

Namely, the narrow frame connection section 414 is configured to includethe first locking surface 423 and the second locking surface 435 andcorresponds to the frame locking section described in “what is claimedis”.

The sixth element abutment section 416 is connected at the front endthereof to the front end of the sixth frame main body section 412 (thefront end of the third narrow frame connection portion 425) and isconfigured so that when the sixth lead frame 353 itself is in a freestate, the sixth frame abutment portion 415 that is an axially rear endportion of the sixth element abutment section 416 is in a state of beingspaced apart from the sixth frame main body section 412. Further, thesixth element abutment section 416 is formed into a circular arc shapewhich is so curved as to allow the space between the axially centralportion thereof and the sixth frame main body section 412 to be largeras compared with the space between the fourth frame abutment portion 315and the sixth frame main body section 412 and to allow the convex sidesurface of the circular arc shape to abuttingly engage an electrodeterminal section of the detection element 4.

In the meantime, the sixth element abutment section 416 is configured toresiliently deform at the front end side end portion and a portionadjacent thereto and continue resilient deformation toward the sixthframe main body section 412 for thereby allowing the sixth frameabutment portion 416 to abuttingly engage the sixth frame main bodysection 412.

Further, the sixth lead frame 353 is configured so that when there is noexternal force applied thereto and the sixth element abutment section416 is not resiliently deformed (when in a free state), the spacebetween the sixth frame abutment portion 415 of the sixth elementabutment section 416 and the sixth frame main body section 412 issmaller than the depth size of the frame disposition groove 286 of thethird separator 282.

In the meantime, the sixth lead frame 353 is configured so that whenplaced between the detection element 4 and the third separator 282 toallow the sixth element abutment section 416 to resiliently deformtoward the sixth frame main body section 412, the sixth frame abutmentportion 415 of the sixth element abutment section 416 is abuttinglyengaged with the sixth frame main body section 412 and at least aportion of the sixth element abutment section 416 is disposed outsidethe frame disposition groove 286 to abuttingly engage an electrodeterminal section of the detection element 4.

Further, the sixth lead frame 353 has a sixth lead wire connectionsection 417 connected to a rear end portion (upper end portion in thefigure) of the sixth frame main body section 412. The sixth lead wireconnection section 417 is formed into a nearly tubular shape by bendingand then caulked radially inward under a condition of having the coreline of the lead wire 46 inserted thereto thereby being electricallyconnected to the lead wire 46 (not shown). In the meantime, FIG. 11shows the sixth lead wire connection section 417 in a state of beingformed into a nearly tubular shape.

As shown in FIG. 10, in case the fifth lead frame 351 is disposed in thethird insertion hole 284, the first wide connection portion 271, thewide protrusion portion 281 and the third wide protrusion portion 381 ofthe fifth lead frame 351 are disposed in the third wide locking groove290 of the third separator 282. As a result, the first locking surface283 of the first wide connection portion 271, the second locking surface285 of the wide protrusion portion 281 and the fifth locking surface 385of the third wide protrusion portion 381 are put into a condition ofbeing engaged with the inner wall surface of the third wide lockinggroove 290.

Further, in case the sixth lead frame 353 is disposed in the thirdinsertion hole 284, the first narrow frame connection portion 421 andthe second narrow frame connection portion 423 of the sixth lead frame353 are disposed in the third narrow locking groove 291 of the thirdseparator 282. As a result, the first locking surface 433 of the firstnarrow frame connection portion 421 and the second locking surface 435of the second narrow frame connection portion 423 are put into acondition of being engaged with the inner wall surface of the thirdnarrow locking groove 291.

In the meantime, the fifth lead frame 351 is disposed in the thirdinsertion hole 284 through insertion into the third insertion hole 284of the third separator 282 together with the lead wire 46 after the leadwire 46 is connected to the third lead wire connection section 267.Further, the sixth lead frame 353 is disposed in the third insertionhole 284 through insertion into the third insertion hole 284 of thethird separator 282 together with the lead wire 46 after the sixth leadwire connection section 417 is connected with the lead wire 46.

By inserting the detection element 4 into the third insertion hole 284of the third separator 282 in a state of disposing therein the fifthlead frames 351 and the sixth lead frame 353 in the above-describedmanner, the third element abutment sections 266 of the fifth lead frame351 can be electrically connected to the electrode terminal sections 30,32, 34, 36 of the detection element 4 and the sixth element abutmentsection 316 of the sixth lead frames 253 can be electrically connectedto the electrode terminal section 31 of the detection element 4.

In the meantime, in the third embodiment, the fifth lead frame 351 andthe sixth lead frame 353 correspond to the metallic terminal membersdescribed in “what is claimed is”, and the third insertion hole 284corresponds to the insertion hole. Further, of the fifth lead frame 351,the first locking surface 283 of the first wide connection portion 271corresponds to the first locking surface described in “what is claimedis” and the second locking surface 285 of the wide protrusion portion281 corresponds to the second locking surface described in “what isclaimed is”.

Further, of the sixth lead frame 353, the first narrow frame connectionportion 421 corresponds to the first frame connection portion describedin “what is claimed is”, the second narrow frame connection portion 423corresponds to the second frame connection portion and the third narrowframe connection portion 425 corresponds to the third frame connectionportion. Further, of the sixth lead frame 353, the first locking surface433 of the first narrow frame connection portion 421 corresponds to thefirst locking surface described in “what is claimed is” and the secondlocking surface 435 of the second narrow frame connection portion 423corresponds to the second locking surface described in “what is claimedis”.

As having been described above, the third air/fuel ratio sensoraccording to the third embodiment has the fifth lead frame 351 with thefirst locking surface 283, the second locking surface 285 and the fifthlocking surface 385, and is configured so that the first locking surface283, the second locking surface 285 and the fifth locking surface 385are abuttingly engaged with the inner wall surface of the third widelocking groove 290.

By such engagement of the first locking surface 283 of the fifth leadframe 351 with the inner wall surface of the third wide locking groove290, it becomes possible to inhibit the third frame main body section262 of the fifth lead frame 351 from moving axially toward the rear endside. Further, by engagement of the second locking surface 285 and thefifth locking surface 385 of the fifth lead frame 351 with the innerwall surface of the third wide locking groove 290, it becomes possibleto inhibit the third frame main body section 262 of the fifth lead frame351 from moving in the direction apart from the inner surface of thethird insertion hole 284.

Further, the sixth lead frame 353 has the first locking surface 433 andthe second locking surface 435, and the first locking surface 433 andthe second locking surface 435 are abuttingly engaged with the innerwall surface of the third narrow locking groove 291.

By such engagement of the first locking surface 433 of the sixth leadframe 353 with the inner wall surface of the third narrow locking groove291, it becomes possible to inhibit the sixth frame main body section412 from moving axially toward the rear end side. Further, by engagementof the second locking surface 435 of the sixth lead frame 353 with theinner wall surface of the third narrow locking groove 291, it becomespossible to inhibit the sixth frame main body section 412 from moving inthe direction apart from the inner surface of the third insertion hole284.

Namely, movement of the third frame main body section 262 of the fifthlead frame 351 and movement of the sixth frame main body section 412 ofthe sixth lead frame 353 can be inhibited even in case an external forceis applied to the fifth lead frame 351 and the sixth lead frame 353,thus making it possible to prevent the relative positions of the fifthlead frame 351 and the detection element 4 and the relative positions ofthe sixth lead frame 353 and the detection element 4 from being varied.

Accordingly, by the third embodiment, a variation in the relativepositions of the lead frame and the detection element 4 can be preventedeven in case an inadequate external force is applied to the lead framesat the time of use of the fifth lead frame 351 and the sixth lead frame353 which are formed smaller in the width side and in the thickness, andthe electrical connection of the lead frames with the electrode terminalsections 30, 31, 32, 34, 36 can be maintained suitably.

As a result, at the time of the assembly work of assembling thedetection element 4, the lead frames and the third separator 282together, buckling of the lead frames is hard to be caused, thereforethe frequency at which a defective is caused in the sensor productionwork can be decreased, and the sensor production efficiency can beimproved.

Then, a fourth wide-range air/fuel ratio sensor (hereinafter alsoreferred to as a fourth air/fuel ratio sensor) with a sixth lead frame353 and a seventh lead frame 511 according to the fourth embodiment willbe described.

In the meantime, since the fourth air/fuel ratio sensor is differentfrom the air/fuel ratio sensor 2 of the first embodiment in that a leadframe and separator are formed into different shapes but other members(metallic housing member, detection element, etc.) are similar in shape,description will hereinafter be made mainly to the lead frame and theseparator.

The fourth air/fuel ratio sensor includes a sixth lead frame 351, aseventh lead frame 511 and a fourth separator 382. The sixth lead frame353 of those constituent parts is similar to that described in the thirdembodiment, so description thereto is omitted herein.

First, the fourth separator 382 will be described.

In FIG. 12 is shown a perspective view of an external appearance of thefourth separator 382 when observed from the front end side thereof. Inthe meantime, in FIG. 12, the fourth separator 382 in the state wherethe sixth lead frame 353 and the seventh lead frame 511 are disposed ina fourth insertion hole 384 is shown in a perspective view.

As shown in FIG. 12, the second separator 382 is formed into a tubularshape having the fourth insertion hole 384 extending axiallytherethrough and has a fourth flange portion 383 protruding axiallyoutward from an external surface thereof. The fourth separator 382 isabuttingly engaged at the fourth flange portion 383 with the outer tubeside support portion 64 of the outer tube 44 and thereby disposed insidethe outer tube 44. In the meantime, the outer tube side support portion64 is formed so as to protrude inward of the outer tube 44 (refer toFIG. 1).

At the inner wall surface of the fourth insertion hole 384, which facesthe first plate surface 21 (not shown) of the detection element 4 areformed two first rib portions 387 that protrude inward. The first ribportions 387 are provided to serve as lead frame boundary portionsinside the insertion hole for forming boundaries of three framedisposition grooves 386 for disposing two seven lead frames 511 and onesixth lead frame 353 separately and in a state of being electricallyinsulated from each other. The three frame disposition grooves 386 areformed at the positions corresponding to the electrode terminal sections30, 31 and 32 at the first plate surface 21 of the detection element 4.

Further, at the inner wall surface of the fourth insertion hole 384,which faces the second plate surface 23 of the detection element 4 (notshown), is formed one second rib portion 389 that protrudes inward. Thesecond rib portion 389 is provided to serve as a lead frame boundaryportion inside the insertion hole for forming a boundary of two wideframe disposition holes 388 for disposing two seventh lead frames 511separately and in a state of being electrically insulated from eachother. The two wide frame disposition grooves 388 are formed at thepositions corresponding to the electrode terminal sections 34, 36 at thesecond plate surface 23 of the detection element 4.

The first rib portion 387 and the second rib portion 389 have a functionof preventing the lead frames disposed in the adjacent frame dispositiongrooves from contacting each other and can prevent the adjacent leadframes from being electrically connected to each other and therebyprevent the electrical path from being deteriorated.

Further, the fourth separator 382 has at the front end surface (thisside surface in the figure) fourth wide locking grooves 390 and fourthnarrow locking grooves 391 that are joined to the front end side openingportion of the third insertion hole 284.

The fourth wide locking groove 390 has a radial groove section that isformed so as to extend from the front end side opening portion of thefourth insertion hole 384 axially outward of the fourth separator 382and an axial groove section that is formed so as to communicate theradial groove section and extend toward the rear end side of the fourthseparator 382. Further, the fourth wide locking groove 390 is formed soas to be capable of disposing therein a seventh frame locking section519 of the seventh lead frame 511, which will be described later.

The fourth narrow locking groove 391 has a radial groove portion that isformed to extend from the front end side opening portion of the fourthinsertion hole 384 radially outward of the fourth separator 382.Further, the fourth narrow locking groove 391 is formed so as to becapable of disposing therein the first narrow frame connection portion421 and the second narrow frame connection portion 423 of the sixth leadframe 353, which will be described later.

In the meantime, the fourth narrow locking groove 391 is formed at aportion connected to central one of the three narrow frame dispositiongrooves 386 that are arranged side by side.

Then, the seventh lead frame 511 will be described.

FIG. 13 is a perspective view showing an external appearance of theseventh lead frame 511. The seventh lead frame 511 is configured so asto be substantially the same as the first lead frame 11 except for aseventh frame locking section 519 that is provided in place of the firstframe locking section 19 of the first lead frame 11. In the meantime,the portions common to the seventh lead frame 511 and the first leadframe 11 are designated by the same references characters as those ofthe first lead frame 11.

The seventh frame locking section 519 is configured so as to include afirst extension portion 131 shaped similarly to the first frame lockingsection 19 and a seventh extension portion 533 having such a shape thatis obtained by enlarging the second extension portion 133 of the firstframe locking section 19 axially toward the rear end side.

Of those portions, the first extension portion 131 is configured so asto extend in the direction of an intervening space between the framemain body section 12 and the element abutment section 16 and in thedirection apart from the element abutment section 16.

Of the seventh frame locking section 519, the first extension portion131 and the seventh extension portion 533 have a first locking surfacethat faces axially toward the rear end side of the frame main bodysection 12 and the seventh extension portion 533 has a seventh lockingsurface 537 that faces in the direction of an intervening space betweenthe frame main body section 12 and the element abutment section 16 andtoward the element abutment section 16 side.

As shown in FIG. 12, in case the seventh lead frame 511 is disposed inthe fourth insertion hole 384 of the seventh lead frame 511, the seventhframe locking section 519 of the seventh lead frame 511 is disposed inthe fourth wide locking groove 390 of the fourth separator 382. As aresult, the first locking surface 135 and the seventh locking surface537 of the seventh frame locking section 519 is put into a condition ofbeing engaged with the inner wall surface of the fourth wide lockinggroove 390.

Further, in case the sixth lead frame 353 is disposed in the fourthinsertion hole 384, the first narrow frame connection portion 421 andthe second narrow frame connection portion 423 of the sixth lead frame353 are disposed in the fourth narrow locking groove 391 of the fourthseparator 382. As a result, the first locking surface 433 of the firstnarrow frame connection portion 421 and the second locking surface 435of the second narrow frame connection portion 423 are put into acondition of being engaged with the inner wall surface of the fourthlocking groove 391.

In the meantime, the seventh lead frame 511 is disposed in the fourthinsertion hole 384 through insertion into the fourth insertion hole 384of the fourth separator 384 together with the lead wire 46 after thelead wire connection section 17 is connected with the lead wire 46.Further, the sixth lead frame 353 is disposed in the fourth insertionhole 384 through insertion into the fourth insertion hole 384 of thefourth separator 382 together with the lead wire 46 after the sixth leadwire connection section 417 is connected with the lead wire 46.

By inserting the detection element 4 into the fourth insertion hole 384of the fourth separator 382 in a state of having disposed therein theseventh lead frames 511 and the sixth lead frame 353 in theabove-described manner, the element abutment sections 16 of the seventhlead frames 511 can be electrically connected with the electrodeterminal sections 30, 32, 34, 36 of the detection element 4, and thesixth element abutment section 416 of the sixth lead frame 353 can beelectrically connected with the electrode terminal section 31 of thedetection element 4.

In the meantime, in the fourth embodiment, the seventh lead frame 511and the sixth lead frame 353 correspond to the metallic terminal membersdescribed in “what is claimed is” and the fourth insertion hole 384correspond to the element insertion hole. Further, of the seventh leadframe 511, the seventh extension portion 533 of the seventh framelocking section 519 corresponds to the second extension portiondescribed in “what is claimed is” and the seventh locking surface 537 ofthe seventh extension portion 533 corresponds to the second lockingsurface described in “what is claimed is”.

As having been described above, the fourth air/fuel ratio sensor of thefourth embodiment includes the seventh lead frame 511 with the firstlocking surface 135 and the seventh locking surface 537 and isconfigured so that the first locking surface 135 and the seventh lockingsurface 537 are engaged with the inner wall surface of the fourth widelocking groove 390.

By such engagement of the first locking surface 135 of the seventh leadframe 511 with the inner wall surface of the fourth wide locking groove390, it becomes possible to inhibit the frame main body section 12 ofthe seventh lead frame 511 from moving axially toward the rear end side.Further, by engagement of the seventh locking surface 537 of the seventhlead frame 511 with the inner wall surface of the fourth wide lockinggroove 390, it becomes possible to inhibit the frame main body section12 of the seventh lead frame 511 from moving in the direction apart fromthe inner surface of the fourth insertion hole 384.

Further, the sixth lead frame 353 has the first locking surface 433 andthe second locking surface 435, and the first locking surface 433 andthe second locking surface 435 are abuttingly engaged with the innerwall surface of the fourth narrow locking groove 391.

By such engagement of the first locking surface 433 of the sixth leadframe 353 with the inner wall surface of the fourth narrow lockinggroove 391, it becomes possible to inhibit the sixth frame main bodysection 412 from moving axially toward the rear end side. Further, byengagement of the second locking surface 435 of the sixth lead frame 353with the inner wall surface of the fourth narrow locking groove 391, itbecomes possible to inhibit the sixth frame main body section 412 frommoving in the direction apart from the inner surface of the fourthinsertion hole 384.

Namely, movement of the frame main body section 12 of the seventh leafframe 511 and movement of the sixth lead frame main body section 412 ofthe sixth lead frame 353 can be inhibited even in case an external forceis applied to the seventh lead frame 511 and the sixth lead frame 353,thus making it possible to prevent the relative positions of the seventhlead frame 511 and the detection element 4 and the relative positions ofthe sixth lead frame 353 and the detection element 4 from being varied.

Accordingly, by the fourth embodiment, a variation in the relativepositions of the lead frame and the detection element 4 can be preventedeven in case an inadequate external force is applied to the lead framesat the time of use of the seventh lead frame 511 and the sixth leadframe 353 which are formed smaller in the width side and in thethickness, and the electrical connection of the lead frames with theelectrode terminal sections 30, 31, 32, 34, 36 can be maintainedsuitably.

As a result, at the time of the assembly work of assembling thedetection element 4, the lead frames and the fourth separator 382together, buckling of the lead frames is hard to be caused, thereforethe frequency at which a defective is caused in the sensor productionwork can be decreased, and the sensor production efficiency can beimproved.

While the embodiments of the present invention have been described asabove, the invention is not limited thereto but can otherwise beembodied variously.

For example, regarding the metallic terminal member having the wideprotrusion portions at the both sides of the second connection portion,the wide protrusion portions need not be of the same protrusion size butcan be different in the protrusion size from one another. This makes itpossible to prevent the rib portion of the separator from becomingpartially too thin and obtain a sensor whose separator is hard to bedamaged. Further, by the provision of two wide protrusion portions, thesecond locking surface can have a large area and movement of the framemain body section can be inhibited even when an inadequate externalforce is applied to the metallic terminal member, thus making itpossible to prevent the relative positions of the metallic terminalmember and the detection element from being varied. Further, since theprovision of two wide protrusion portions makes it possible to preventthe metallic terminal member from going apart from the inner surface ofthe element insertion hole of the separator more assuredly, buckling ofthe metallic terminal member at the time of insertion of the detectionelement into the element insertion hole of the separator can beprevented.

Further, in order to maintain the rotational position of the separatorrelative to the outer tube constant, the separator may be formed with anengagement portion for positioning. By engaging the engagement portionfor positioning with a predetermined engagement portion of the outertube, the rotational position of the separator relative to the outertube can be maintained constant. As an example of the engagement portionfor positioning can be enumerated a cut portion 181 shown in FIG. 8.

Further, for engagement of the frame locking section of the metallicterminal member with the separator, the separator may be formed with apartition wall located between the frame locking section and the elementinsertion hole without being formed with the locking groove so that theframe locking section is engaged with the partition wall. In themeantime, it is not necessary to form the partition wall in place of thelocking groove but together therewith.

Further, the sensor to which the present invention is applied is notlimited to a sensor formed with the electrode terminal sections by fivebut the present invention can be applied to a sensor having an detectionelement with four electrode terminal sections or less or six electrodeterminal sections or more.

1. A sensor comprising: a detection element in the form of an axially extending plate, having a front end side to face an object to be measured and formed with an electrode terminal section at a rear end side; a separator made of an insulating material and having an element insertion hole accommodating the rear end side of the detection element; and a metallic terminal member interposed between the detection element and an inner surface of the element insertion hole of the separator; characterized in that: the metallic terminal member is formed from a metallic sheet material and includes an axially extending frame main body section, an element abutment section extending while being bent to change the direction of extension, from a front end of the frame main body section axially toward a rear end side of the frame main body section and contacting the electrode terminal section of the detection element thereby being electrically connected thereto to form a current path, and a frame locking section provided to a portion of the frame main body section and having a larger width than a remaining portion of the frame main body section; and the metallic terminal member is disposed within the separator so as to be put in a state of being engaged at the frame locking section with the separator.
 2. A sensor according to claim 1, wherein the frame locking section has an extension portion that extends in the direction apart from the element abutment section and is bent at least once or more at an intermediate part thereof in a way as to change the direction of extension, the fame locking section being larger in width than the remaining portion of the frame main body section when the extension portion is developed in the width direction of the remaining portion of the frame main body section.
 3. A sensor according to claim 1, wherein the separator includes a locking groove for engagement with the frame locking section.
 4. A sensor according to claim 3, wherein the locking groove is formed at a front end surface of the separator.
 5. A sensor according to claim 1, wherein the separator includes a partition wall portion disposed between the element insertion hole and at least a part of the frame locking section.
 6. A sensor comprising: a detection element in the form of an axially extending plate, having a front end side to face an object to be measured and formed with an electrode terminal section at a rear end side; a separator made of an insulating material and having an element insertion hole accommodating the rear end side of the detection element; and a metallic terminal member interposed between the detection element and an inner surface of the element insertion hole of the separator; characterized in that: the metallic terminal member is formed from a metallic sheet material and having an axially extending frame main body section, an element abutment section extending while being bent to change the direction of extension, from a front end of the frame main body section axially toward a rear end side of the frame main body section and contacting the electrode terminal section of the detection element thereby being electrically connected thereto to form a current path, and a frame locking section provided to a portion of the frame main body section; and the separator has a locking groove at a front end surface thereof and the frame locking section is engaged in the locking groove.
 7. A sensor comprising: a detection element in the form of an axially extending plate, having a front end side to face an object to be measured and formed with an electrode terminal section at a rear end side; a separator made of an insulating material and having an element insertion hole accommodating the rear end side of the detection element; and a metallic terminal member interposed between the detection element and an inner surface of the element insertion hole of the separator; characterized in that: the metallic terminal member is formed from a metallic sheet material and having an axially extending frame main body section, an element abutment section extending while being bent to change the direction of extension, from a front end of the frame main body section axially toward a rear end side of the frame main body section and contacting the electrode terminal section of the detection element thereby being electrically connected thereto to form a current path, and a frame locking section having a first locking surface facing axially toward a rear end side of the frame main body section and a second locking surface facing in the direction of an intervening space between the frame main body section and the element abutment section and toward the element abutment section; and the separator has a locking groove for disposition of the frame locking section and engages at an inner wall surface of the locking groove with the first locking surface and the second locking surface.
 8. A sensor according to claim 7, wherein the locking groove is formed at a front end surface of the separator.
 9. A sensor according to claim 7, wherein the metallic terminal member is configured so that a frame abutment portion of the element abutment section, which is positioned closer to a rear end of the frame main body section than an end portion of the element abutment section, which is connected to the front end of the frame main body section, is not abuttingly engaged with the frame main body section when the metallic terminal member is in a free state before being electrically connected to the electrode terminal section of the detection element, while the frame abutment portion is abuttingly engaged with the frame main body section when the element abutment section is electrically connected to the electrode terminal section and resiliently deformed toward the frame main body section.
 10. A sensor according to claim 1, wherein the frame locking section includes a first connection portion extending from a front end side portion of the frame main body section in the direction apart from the element abutment section, a second connection portion extending from an end of the first connection portion on the side remoter from the element abutment section, axially toward the front end, and a wide protrusion portion protruding from the second connection portion in the width direction of the second connection portion, and wherein the first connection portion is formed with the first locking surface, and the wide protrusion portion is formed with the second locking surfaces.
 11. A sensor according to claim 10, wherein the wide protrusion portion is formed so as to be asymmetrical about a center axis of the second connection portion.
 12. A sensor according to claim 7, wherein the frame locking section includes a first extension portion extending from a front end side portion of the frame main body section in the direction apart from the element abutment section and a second extension portion extending from an end of the first extension portion on the side remoter from the element abutment section in parallel with the frame main body section, and wherein at least one of the first extension portion and the second extension portion is formed with the first locking surface and the second extension portion is formed with the second locking surface.
 13. A sensor according to claim 12, wherein at least two of the frame locking sections are provided so as to extend from different places of a front end side portion of the frame main body section.
 14. A sensor according to claim 7, wherein the frame locking section includes a first frame connection portion extending from a front end side portion of the frame main body section in the direction apart from the element abutment section, a second frame connection portion extending from an end of the first connection portion on the side remoter from the element abutment section, axially toward a rear end side of the frame main body section, and a third frame connection portion extending from an end of the second connection portion on the side opposite to the side for connection with the first frame connection portion so as to be connected to the element abutment section, and wherein the first frame connection portion is formed with the first locking surface and the second frame connection portion is formed with the second locking surface.
 15. A method of producing a sensor including a detection element in the form of an axially extending plate, having a front end side to face an object to be measured and formed with an electrode terminal section at a rear end side, a separator made of an insulating material and having an element insertion hole accommodating the rear end side of the detection element, and a metallic terminal member interposed between the detection element and an inner surface of the element insertion hole of the separator, wherein the metallic terminal member is formed from a metallic sheet material and having an axially extending frame main body section, an element abutment section extending while being bent to change the direction of extension, from a front end of the from the frame main body section axially toward a rear end side of the frame main body section and contacting the electrode terminal section of the detection element thereby being electrically connected thereto to form a current path, and a frame locking section having a first locking surface facing axially toward a rear end side of the frame main body and a second locking surface facing in the direction of an intervening space between the frame main body section and the element abutment section and toward the element abutment section, wherein the separator has a locking groove for disposition of the frame locking section, the method being characterized by comprising: a first step of disposing at least the element abutment section of the metallic terminal member within the element insertion hole of the separator and disposing the frame locking section within the locking groove, thereby engaging the first locking surface and the second locking surface with the inner wall surface of the locking groove; a second step of disposing the rear end side of the detection element, at which the detection element is formed with the electrode terminal section, at a front end side of the separator; and a third step of inserting the rear end side of the detection element into the element insertion hole of the separator and bringing the electrode terminal section of the detection element and the metallic terminal member into contact with each other.
 16. A method of producing a sensor according to claim 15, wherein the metallic terminal member is configured so that a frame abutment portion of the element abutment section, abutment section, which is positioned closer to a rear end of the frame main body section than an end portion of the element abutment section for connection with the front end of the frame main body section, is not abuttingly engaged with the frame main body section when the metallic terminal member is in a free state before being electrically connected to the electrode terminal section of the detection element, while the frame abutment portion is abuttingly engaged with the frame main body section when the element abutment section is electrically connected to the electrode terminal section and resiliently deformed toward the frame main body section, and wherein the first step includes disposing the metallic terminal member in a state of not receiving any external force within the element insertion hole of the separator and the third step includes inserting the detection element into the element insertion hole while pushing the detection element against the element abutment section, thereby resiliently deforming the element abutment section toward the frame main body section and abuttingly engaging the frame abutment portion of the element abutment section with the frame main body section. 